Hi, I'm not Jin, but I can help.
First things first, clean the miniatures with dish soap, or use dishwasher soap if you're hardcore (and use gloves if you do, because you will regret it if you don't). Scrub them with something like a toothbrush. You've gotta get off any oily residue that might be present.
Rinse them well afterwards, and let them air dry.
Once that's done, prime them with Tamiya spray primer (grey or white). Tamiya primer is handy because it works well with pretty much any plastic. Some primers are too hot and will eat the plastic.
Okay, now you're ready for painting. I like Vallejo acrylic paints for hand painting. Most of the Vallejo line can be brushed without any thinning, but make sure you shake them well before use. If you want to thin them, use an eyedropper and water.
Always clean your brushes well after use. As for brushes, pick a large brush, a medium-sized squarish brush, a small one and a small one with a pointed tip. You can do some reading later if you'd like to learn about brushes.
Go to a hobby shop, they may be able to help.
