Rick: yes, U made me do it. I“m happy that you pushed me in the right direction - it wasn“t that hard anyway.
Thx All for the nice comments!
I used a standard tamiya putty, applied thinly. I let i dry for a few seconds (its fast curing) and then i shaped it with a screwdriver (keep it clean and moist).
Finaly I stroked it with a brush of humbrols liquid poly to get a more even surface.