Is plastic fouling such a problem that it can affect the performance of a gun and, if so, in what way? Should I use the solvent each time I use the gun?
Gun cleaning advice
I used to have a gun that suffered quite badly from plastic fouling, and I used to get it out with Hoppes No.9 rifle barrel cleaner, although there are doubtless other preparations which are equally effective.
How do you know you have plastic fouling in the first place?
Well, after cleaning with a conventional solvent followed through by a dry patch on a jag, the insides of the tubes should be mirror-bright. If they look grey, then it could be plastic.
With a suitable solvent, the plastic fouling often comes out looking like horrible, slimy stuff on your bronze brush. use the solvent every time you suspect plastic is present in the bores.
I dont know the composition of the preparation you are thinking of using, but remember that rifle barrel cleaner is designed to remove metallic fouling, and it will also start to attack your bronze brush, so wash the brush carefully after use.
The real danger of plastic fouling is that it is acidic, and can promote rust in bores which are not chrome plated.