Any 2 part paint has a "glue" effect ( aside from a basecoat) and will "eat" some of the plastic.
>> 2ManyT/A's<< is on the right track ( nothing new there!!
)
First Use a product like DX330 ( clean strip makes a cheaper one, paint pre prep) Do NOT use a soapy water based product in a plastic bottle at autozone)
Then use a "Adhesion promoter" ( I use bulldog brand by kleen strip) Follow directions, you only let it sit for a few MINUTES before your color.
Then apply your "made for plastic" SEM coatings AS the DIRECTIONS say. You cannot lay on huge wet coats.
Good luck!! I have done many with plenty of success.. On chalky panels its a crap shoot