Shotgun cleaning. A topic near and dear to my heart.
In the old days, when all I used to shoot was feathery things and maybe go through 8-10 boxes of shells a year, I’d never heard of / noticed any plastic wad fouling. Now with all the family shooting clay target sports I’ve quickly learned that plastic fouling is a big deal. Especially when you go through a flat of shells on a hot summer day. My pattern testing shows that (in my gun and choke, at least) a plastic-fouled barrel patterns much worse than a clean one.
Thus for solvent I highly recommend Shooters Choice Shotgun and Choke Tube Cleaner. Look for it in the yellow can with the green lightning bolt, and the words, “Quickly melts plastic wad fouling!” (It does just that.) Spray it down the detached barrel (outdoors ... the smell is very strong), let it soak a bit, and then push through a big cotton “patch” make out of an old tee shirt or tighty whities. Push that patch straight into your garbage can because you aren’t going to want it again. If you’ve got wad fouling it’s going to come out the other end with godawful strands of goopy, dissolving plastic. Push through another dry patch, then one coated in your favorite CLP for rust prevention, then a dry one again to wipe out excess CLP.
If my choke is really fouled I’ll take it out and pre-soak it with Shooters Choice, then scrub with a bronze brush before proceeding as above. Use a toothbrush and some CLP to clean the choke threads in the barrel. And be sure to put some Outers choke tube grease on the threads before reinstalling or you may turn it into a fixed choke gun. Don’t ask me how those damn things stick so badly if not greased.
For a cleaning rod I recommend a big wooden dowel. Especially good for a long, 34” trap barrel with an extended choke to boot; most factory rods won’t reach that far. If you can find a proper, heavy gauge shotgun cleaning rod, even used on eBay, jump on it. Most new rods are simply narrow ones like you’d use for a rifle, but with an adapter to thread on a shotgun brush. Kinda wimpy for heavy use.
Clean and lube the receiver like you would a pistol with a very light CLP coating.
On modern “field grade” shotguns they have abandoned nice glossy bluing in favor of the rough parkerized sort of finish. Used to only be the Remington 870 Express that was finished like that, but now even guns up to $1000 like the Beretta A300, Franchis, and the Remington V3 are rough textured. Rust can form down in there. So for those I really love a full Froglube treatment, especially if they’re going to be out in the rain, humidity, etc. I’ve done a lot of rust testing on metal samples misted with saltwater and left outside, and nothing beats Froglube for rust prevention. Down side: the aggressive barrel cleaner with strip the Froglube away, so for my barrels I clean inside first then reapply Froglube again on the outside.