The easiest way I've found to remove plastic fouling is to spray the bbl with WD-40 and let it sit overnite. The WD-40 loosens the plastic and it brushes out easily the next day. Kroil, Liquid Wrench, and other penitrating oils will work also but the WD is much cheaper, and smells better. I spray enough in the bbl that it drips out the other end, actually spraying from both ends works best. Wrapping a brush with 0000 steel wool and spinning it with a drill will also work, but messy. Use the WD-40 to spary your brush clean after use.
If you reload you can coat/dust your wads with Motor Mica before loading to reduce the fouling but nothing I know of eliminates it, other than not using plastic wads which is not a realistic option anymore. You'd sacrifice performance to eliminate plastic fouling. That's a poor trade off.