Brandon
Hisayo takes the senbon and looks it over. It's a fairly simple shape, at least - thin, with a taper at the ends. The sharpness is probably going to be the most difficult thing; cutting and piercing is often the expertise of Wind techniques. Hisayo isn't going to get anywhere by simply staring at it, though, so after a few moments of looking it over, she hands the needle back to Chinami and weaves through some hand seals. 

It's not perfect at first, but what is? Hisayo's mouth fills with water, which she attempts to channel down into fine, sharp needles and then spit towards the ground, away from Chinami. What comes out are... Shorter, flatter shapes of inconsistent size. Hisayo has the *Idea*, at least, but maybe she needs a bit more practice - or advice. Or experience in forming water chakra.
Catalina
*Chinami looked as Hisayo attempted to perform the technique. She had to admit what she saw is what she expected, it was a very common problem but luckily it had a simple solution*

"It looks like you are trying to almost force the water into the correct shape. If you do that it will never work, at least not until you are a master of water release. What you want to do is take less water and stretch it out, if you do it this way it will automatically get sharper as it stretches. Give it a shot."
Brandon
Hisayo sighs. "You are correct; I suppose I am more used to having to marshal wind chakra into shape rather than form water chakra. Wind chakra is... *Flighty*, it refuses to properly stay in place unless forced, and even then it resists confinement as soon as it is dispatched, so to speak." With that, Hisayo works the last bits of water out of her mouth and contemplates a second attempt at the jutsu. Less water and stretch it out... Like a raindrop. Like needles of rain blown sideways through a storm, stinging those that it strikes. And then even further, to the point where it might pierce their skin and wound their muscles.

With that conceptualized, she begins to make her way through the hand seals once again. She focuses more closely on the chakra transformation, and makes certain not to over-use energy when she's transferring it through her body to the appropriate exit tenketsu. Hisayo's reserves are deep, but more is not always better; she sometimes finds herself overdoing jutsu, which results in it coming out sloppily. For large amounts of chakra, equally large amounts of control are necessary. 

Her mouth begins to fill with water, but a smaller amount this time, trickling across her tongue, easier to manipulate. One by one, more deliberately, she stretches a small amount of the chakra-infused fluid into a sharp, hard needles, making completely certain to apportion each only the necessary amount of chakra to keep their integrity. One, two, three, four... The senbon begin to take up space in her mouth, until she's finally ready for the next step.

Once again, Hisayo turns her gaze downwards, and spits. This time, light blue needles shoot from between her lips and embed themselves into the ground before being absorbed. The spot between her and Chinami is peppered with little holes; not quite as large or in as focused of a spread as if an expert in Water Release had used the jutsu, but a passable attempt for certain.

Hisayo crouches down to inspect the impact the needles made, confirming their relative lack of power, and then glancing up at Chinami. "Well, I suppose that was a better try. Enough to pierce skin, certainly, though I think I will need some additional independent practice." She works her mouth about, trying to find that last little bit of excess water that's made its way into the corner - that always seems to happen when she works with water release. If Chinami has any further criticism or advice to offer, Hisayo will absolutely hear it out.