Molleur:
Wurth used to have a product called Body Schutz, stays flexible and can be painted over. Also I have used a 3M product, don't remember the name but the can screws onto the applicator gun (About $60) and it can be built up rather thickly.
No mixing required on the 3M stuff, just spray it on and you can also paint over it.
Both come in black as far as I have seen.
Good Luck
Phil