Thanks to your great help, I managed to stick on the decals and the result is great. Here is what I did:
- clean the frame surface with acetone (do not use on paint!) This will dissolve traced of dirt
- dry the surface with a paper towel
- clean the surface with rubbing alcohol (isopropylalcohol) and dry the surface with a microfiber cloth that is used for glasses. This will also dissolve dirt and degrease, but doesn't leave traces like acetone.
- stick two strips of scotchtape magic on the long sides of the decal.
- firmly press on the decal, starting in the middle, pressing it on towards the edges, where the scotchtape keeps it in place
- press the decal further on with a piece of paper towel
- rub the decal on with a wooded dowel or spatula, paying extra attention to the edges
- keep rubbing with the wooden spatula or dowel, but be careful not to damage the backing
- afer five minutes of carefull rubbing: remove the scotchtape on an edge and peel of the backing very carefully
- if the decal is on the frame, continue removing the backing
- if the decal is still on the backing, press the decal back into place and continue rubbing the edges
- when the decal is in place and the backing removed, softly press othe decal with a microfiber cloth
Secret of success: patience. Eventually the decal will let go of the backing and stick to your frame. It may help to gently heat the frame prior to sticking the decal on with a hair dryer.
(also published on Fatcogs)