Lots of questions there, my friend. Fortunately, there are lots of answers in similar projects posted on the forums already. I think that the reason no one has replied in two days is because you asked a bunch of questions. Do some research, post those questions one at a time, and people will probably be more forthcoming with answers.
I had good luck cutting, assembling, and painting my ABS plastic trim pieces using an epoxy putty (sounds similar to the stick you're describing), lots of sandpaper, Krylon automotive primer, a red bondo filler paste, more sanding and primer, and a lacquer-based color matched top coat. A few pics are in my worklog...link is in the sig.