I use enamel paints. Out of the 3 types of paints you encounter in modeling, enamels, lacquers and acrylics. Enamels and lacquers are the most durable, but ver toxic, use HIGH ventilation. Lacquers are very difficult to find though, you pretty much have to order them from Japan. Acrylics aren't as durable, but a lot less toxic to use(windex/soap and water to clean). Wear a respiration/filter mask whenever painting.
Aside from the durability of the paints, you really have to pay special attention to areas where the parts rub against each other. Sand those areas down (knees, wing housings, inside chest for the heatshield, arm joints, leg joints etc...) If you're uncertain, prime first, than put the valk back together and than transform it, it'll show you which areas needs attention and fixing.