what will stick to plastic?

I'm working on modifying my stock rear panels in my integra.  The problem is that glass wont stick to the abs plastic.  From previous experience, I found out that if you ruff up the plastic good, put on a layer of bondo glass, then fiberglass over the top of that, then it will stick.  Anyway, I dont want to glass my whole panel...just a small addition, which successfully stuck from the above process.  But my question is how do i feather in the plastic to the glass?  Is there some kind of liquid plastic like JB Weld or something that i can use for the transition that will stick to both surfaces and be able to sand out smooth?  I tried the half bondo/half resin mix and that didnt stick to well so any ideas are appreciated.

try using PLastic weld or Duramix.. it works real well.. make sure u sand surface.