How to practice Metta without a Benefactor? I find it very difficult to practice metta because i can't find anyone who has been a benefactor.I don't know a lot of people.Most people i know i find it very difficult to send metta to as a benefactor as their either very dear to me or downright hostile.Can i just imagine a benefactor i never had .Or use a dead person, as my auntie was very kind to me but she's deceased now.

How can i practice metta without a benefactor? How can i find a benefactor to practice metta to?
You don't need a benefactor to practice that type of metta; you just need someone who is dear to you;  it just shouldn't be someone you could potentially desire sexually, or whom you are partial towards, like your children. 

The stages, according to the Visuddhimagga are as follows:


cultivate metta towards yourself (useless, but a good example)
cultivate metta towards someone you hold dear
cultivate metta towards a neutral party
cultivate metta towards someone you dislike (optional, only for those who have such a person)


Having someone dear to you seems important, as there is no advice given for what to do if such a person does not exist. Ostensibly, you could skip that step and try to immediately cultivate metta towards a neutral party, but the dear one is useful for returning to when difficulty arises with the other objects.

Alternatively, you could try cultivating metta in order of proximity; may I be happy, may all beings in this room be happy, this building, this city, this country, this world, the universe. Also, by direction; may all beings to the East be happy, etc. Or finally, by class: may all women be happy, men, animals, angels, etc.

Mahasi Sayadaw has a detailed exposition of the four brahmaviharas that is both practical and informative:

http://static.sirimangalo.org/mahasi/Brahmavihara%20Dhamma.htm

As he says, 


  "Mettā can also be developed towards any other person deserving of affection and respect, if not towards your teacher, grand-parents, mother, father and so on."