italian camou

Well, did mine freehand :) but I've also heard of folks spraying the base coat, spraying the overall "ring" shape, then filling in the center with the base coat again.

Not sure how they manage to avoid "tinting" the base color in the center of the rings....

Draw some shapes on a sheet of paper and cut them out like a stencil. Hold them back a little and that should give you a soft edge. Try it on some scrap first to see if it gives you what you want.