>>10601847This isn't TVC but BS, the plastic won't be any different though. Just use water or isopropyl alcohol to thin your paint and work in layers, letting each one dry in between to build up sufficient opaqueness. The tricky part is joints, as you usually usually will need to sand a bit of the joint surface down so that way when you apply paint, you won't get any paint rubbing off when you actually use the joint.
If you're wanting to repaint those troopers then that's pretty easy. Just use masking tape to do the stripes on the limbs and I would just find some 1/18 waterslide decals to do the cogs on the shoulders.