Solvent is one of the worst options for "shining" polymers. They either swell the material, dissolve the surface into a sticky mess, or, worst case, allow the material to crystallize. Plexiglas type polymers become hazy with a single drop of acetone. A bit of jeweler's rouge should do the trick polishing. You can try heat, but that requires practice, and a gun frame is probably not what you want to use as your first practice piece.
F 135 - the right choice