Which companies use paint the best and the worst? ThreeZero seem to be pretty decent with the paint on their figures (from what I've seen at least), whilst on the more affordable end of the spectrum Bandai scores points for smart and well-applied paint apps, and 4H does some pretty amazing and high quality paintjobs with very few errors.
Some of the worst, aside from obvious offenders like McFarlane, NECA and ToyBiz (when they existed) would be Squeenix. Their promotional pics look amazing but the figures nearly always look like complete crap when they come out for some reason.