What he said. You have listed my top two most useful modelling materials, but they are for completely different purposes. Plasticard will be your best bet for model conversions. If you're having trouble with shattering or snapping, try multiple layers of bent pieces of a thinner thickness. Or try your hand at the boiling water/hot salt/etc methods to make shaping a little easier.
As for your paint range question, try this:
http://www.dakkadakka.com/wiki/en/Paint_Range_Compatibility_Chart