Hi Stefan
I have used a couple of times
Finespray Fine Line Green Tape.
This tape is an automotive tape used for spraying lines on cars. Not only straight but curved. But not as curvy as we sometimes have on small scale models.
Found it worked well. Very stretchable & easy to remove. Problem is that with any tape you have the paint sticking to both tape & model homegenously. Tried on the last cockpit cover painting to gently score with a fresh Morton blade along the tape line & this provided a better separation. Not sure how this would work/look on paint on paint.
As Steve (Stona) made the point in another article recently it is the strata you are painting on which provides the difference. After reading this I looked at
decals which stayed silver after pricking multiple klear coats etc & sure neough the paint base was not as good as it should be.
Laurie