Electrical tape will completely change the way you mask off projects in the future. It's stretchy, sticky, flexible and keeps out the paint VERY well. Perfect for turning corners and round areas.
Plus it's cheap.
I wondered about electrical tape but wasn't sure if it would tear off paint that was already there.
I use a type of tape at work, we just call it "z tape". Its a little thinner than electrical tape but basically the same. I've been wanting to try that cause it will stretch better but it sticks more than electrical tape.
3M also makes a few automotive masking tapes for doing flame jobs and things like that. Bit pricey, but works well. Basically use the thin tape to mask off the curve, then build up the rest of the mask with larger bits of tape once you've got the contour's outline masked off.