When masking a line that is very tight don't use the outside/inside edge of the tape, it can be irregular and cause imperfections in the line you are trying to make. Instead cut the tape down with an X-acto knife, creating a razor sharp edge to mask with. I just tear off a piece and stick it on some clean plexi, then use my metal straight edge to shave off a few mm from one or both edges of the tape. If you have to mask some compound curves or flames, use tape that is about 1/8" in width, if you can't find tape this size cut some down like mentioned above. Thin tape will bend and flex into a curve easily.