Sorry to necro this thread..
A number of you have said you used SEMs adhesion promoter but there are different kinds of adhesion promoters.
I have this document called SEM training manual. Within it says to use 3836(x) SAND FREE for ABS and PVC. It says to use 3986(x) or 7772(x) for TPO, EDPM, PP and other similar thermoplastics. To tell the difference, it says acetone will melt/smear the former and not the latter. The door panels from my 79 and 84 don't seem to be affected by acetone. Problem is I can get the 3836 locally but I'm having trouble sourcing the latter two.
So specifically which adhesion promoter have you used or better yet, what type of plastic are the factory door panels?