Some drops come out of him after urinating, but if he waits he may miss the prayer in congregation
Question

                My question is about madhiy (prostatic fluid). When it comes out, I do ghusl, then I go to pray, but when I come back to the washroom – please excuse me – I find some remaining drops coming out with the urine, and sometimes I stay in the washroom for more than half an hour to make sure that all of it has come out. My question is: should I make sure that it has come out completely, or should I do ghusl then go to pray? Please note that sometimes I miss some of the prayers in the mosque for this reason, and sometimes I remain uncertain, in that I go to the mosque and pray then come back and I am still not sure whether I was in a state of purity, so I offer the prayer again at home.
Praise be to Allah.
    Firstly: 

    What comes out following urination is usually wadiy, which is 
    a thick, white liquid that comes out in the form of drops. As for madhiy 
    (prostatic fluid), it is what comes out following provocation of desire. 

    Both of them invalidate wudoo’, but they do not necessitate 
    ghusl. When you say, “When it comes out I do ghusl”, perhaps you mean that 
    you wash it. As for ghusl (full ablution), you do not have to do it; rather 
    you have to do wudoo’. 

    An-Nawawi (may Allah have mercy on him) said, explaining the 
    difference between madhiy and wadiy: As for madhiy, it is a sticky, thin, 
    clear fluid that is emitted with or without desire; it does not gush out in 
    spurts, and it is not followed by exhaustion; and one may not feel it coming 
    out. It happens to both men and women. 

    As for wadiy, it is a thick, darkish fluid that resembles 
    maniy (semen) in its thickness, but differs from it in colour, and it has no 
    smell. It comes out following urination, when one is constipated, or when 
    carrying something heavy, and it comes out in the form of one or two drops 
    and the like. The scholars are unanimously agreed that it is not required to 
    do ghusl when madhiy and wadiy are emitted.

    End quote from al-Majmoo‘, 2/160 

    Shaykh Ibn Jibreen (may Allah preserve him) was asked: At the 
    end of urination, I notice some seminal fluid (maniy) coming out, and I do 
    not know whether I have to do ghusl every time I urinate, or what should I 
    do? Because I am not sure whether it has the same effect as intercourse? 

    He replied: This “maniy” that comes out after urination is 
    wadiy, which is well known (and is not actually maniy). As it comes out 
    after urination and comes out in a stream (as opposed to gushing out), it 
    does not necessitate ghusl. However it does invalidate wudoo’, so the penis 
    should be washed after that, then one should do wudoo’, but it is not 
    necessary to do ghusl. Ghusl is only required when maniy gushes out in 
    spurts accompanied by feelings of pleasure, and is not required otherwise. 
    As gushing out in spurts forcefully is not like the emission of urine, which 
    comes out in a stream or in drops, it does not matter if it comes out like 
    that.

    End quote from Fataawa Islamiyyah, 1/226 

    Secondly: 

    When you have relieved yourself, you have to wait until you 
    are certain that the flow has stopped, then clean yourself and do wudoo’. If 
    that leads to you missing the prayer in congregation, there is no blame on 
    you. But you should get ready for the prayer before the time comes, so long 
    as you know that you need a long time to relieve yourself. 

    The Standing Committee for Issuing Fatwas were asked: There 
    is a man who suffers from urinary incontinence. He purifies himself some 
    time after urinating, but if he were to wait until the incontinence ends, 
    the time for the prayer in congregation would be over. What is the ruling? 

    They replied: If he knows that the incontinence will end, it 
    is not permissible for him to pray when it is still affecting him, seeking 
    the virtue of praying in congregation. Rather he has to wait until it ends, 
    then he should clean himself after that, then do wudoo’ and offer his 
    prayer, even if he misses the prayer in congregation. However he should 
    hasten to clean himself and do wudoo’ once the time for the prayer has 
    begun, in the hope that he will be able to pray in congregation. End quote. 

    Fataawa al-Lajnah ad-Daa’imah, 
    5/408 

    Shaykh Ibn Jibreen (may Allah preserve him) said concerning 
    the one who is faced with that problem: 

    First of all you have to take precautions with regard to 
    purification. So do wudoo’ half an hour or so before the time for prayer 
    begins, after you have urinated and the effects of urination have ceased, in 
    the hope that it will stop before the time for prayer comes. 

    Secondly, after urinating you have to wash your private part 
    with cold water that will stop urination and prevent drops coming out. 

    If these drops are the result of waswaas (whispers from the 
    Shaytaan) or something imaginary, then after cleaning yourself you should 
    sprinkle water on your pants or thobe, so that the Shaytaan cannot make you 
    imagine, if you see dampness, that it is urine, because you will know that 
    it is water that you put on your garment.

    End quote from Fataawa Islamiyyah, 1/196 

    Thirdly: 

    You should beware of waswasah (whispers from the Shaytaan), 
    for it is a disease and an evil that can cause a person to worry and 
    generate doubt in his mind, making worship burdensome for him. So beware of 
    that. When you have relieved yourself, done wudoo’ and prayed, do not pay 
    any attention to doubts, because the basic principle is that one is pure and 
    that prayers are valid. 

    Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) was 
    asked: When I have finished wudoo’ and am going to pray, I feel a drop of 
    urine coming out of the penis; what should I do? 

    He replied: 

    The one who is affected with that should ignore it, as 
    enjoined by the leading scholars of the Muslims. He should not pay any 
    attention to it or go and check whether anything came out or not. By Allah’s 
    leave, if he seeks refuge with Allah from the accursed Shaytaan and ignores 
    it, it will go away. But if he is utterly certain about it, then it is 
    essential to wash whatever the urine has gotten onto, then repeat his wudoo’ 
    because some people, if they feel coldness at the tip of the penis, think 
    that something has come out. But if you are certain, you should do what I 
    told you. What you have mentioned is not incontinence, because it stops, 
    whereas incontinence is ongoing. As for this, it is one or two drops that 
    come out after moving; this is not incontinence because two drops come out 
    then it stops. In this case you should wash yourself and do wudoo’ again. 
    You should always do this, and be patient and seek reward with Allah.

    End quote from Liqa’ al-Baab al-Maftooh, 184/15 

    And Allah knows best.