Another AutoBody question.. (ABS Plastic Painting)

I've made some fiberglass door panel add-ons to attach to my OE panels (ABS Plastic).. 

I have successfully attached the FG panels to the OE ones using rivets and panel adhesive.  

now  I am trying to mold them together and just realized that bondo dosen't adhere well to ABS.  

So the question is, what do your experienced autobody guys use as a filler on ABS plastic since bondo isn't the best..

I was thinking of spraying epoxy primer or 2k primer over the scuffed up ABS surface...  then working bondo on top of that primer.  


any ideas, leasons learned tips, etc.. would be appreciated.

just an idea of where i started.. and what i'm trying to mold to the OE ABS plastic door panels..
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see pics 1-4

1. foam shape
2. foil over the shape. 3M spay glue used to adhere foil to shape
3. fitting FG cloth
4. applying resin
5. trim and add more FG mat to the back.. etc.. (no pic)

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i got the idea to make these door panel add-ons from other DIY posts in this forum
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