The answer for a cover is go offshore 100 miles. buy Can, cover with a duffel bag.
By the powers we live with in California, if I take just one decibel away from my gun discharge, that is illegal. I don't work for the government and am not allowed to be illegal.
Watching can's being made on Youtube looks pertty straigt forward.
I had a friend who thought putting a potato over the muzzle of a gun was a good hill billy muffler.
I've seen barrels blow up and personally would rather go with the noise.