On compound curves I mask with the narrowest tape I have. I have some of the Tamiya 6mm stuff, and Pactra even has 1/16 width. Then I use regular masking tape to cover more extensive areas, but the narrow stuff follows the curves nicely.
Sometimes, when it is neccessary to paint around very small details that are dark colors, but the detail has either raised or engraved "panel" lines, I put a piece of masking tape over the area and use a brand new #11 blade in my hobby knife and trace around the panel or whatever, leaving the cutout piece to mask the panel or part.