My first choice in solvents for general cleaning, is Mineral Spirits. It will clean and so far, have not seen it harm anything associated with firarms. Your Hoppe's cleaning solvent should be okay on plastice but try it on a small area, to confirm. ....
I have seen Carb. cleaner damage some plastics. Brake cleaner is safer than Carb. but still pretty strong. I save my brake cleaner for the really nasty metal cleaning and the spray is strong and will blow the junk out of hard to reach places. ....
Be Safe !!!