I 'crack' the klicky for painting, too.
For the arms, I use a Playmo spear to secure them ... the hands klick on nice and tight, making them easy to paint.
For the legs, I use a Q-Tip (cotton swab). The cotton seems to hold the legs relatively still while I paint.
For the main body, I use a bit of Fimo clay on a bamboo skewer, then secure the torso on top of that. Warning: the enamel paint NEVER dries on the clay, so be careful when removing the playmo piece, so you don't pick up paint from the clay on your fingers. I use another bamboo skewer through the arm holes to pull it away, just in case.
I highly recommend using a GOOD quality paint brush. The brushes are expensive, but they're worth it.
I use enamel paint, too. I don't think your acrylics will work as well, Psyche. I'm used to them as well, but you're not going to get the coverage you want on the plastic without adding too much thickness. Believe it or not, that paint thickness will get you.