When any object (airplane or bullet) approaches transonic speed it passes through it's own "Precursor" wave, (think the bow wave from a boat only in air) and experiences buffeting from the shockwave as it passes through. Subsonic rounds never experience this buffeting and are usually more accurate because of it.
I rinse mine out with sprayable Hoppe's and stand on end on some newspapers, after about a half an hour turn it over. Or get some CCI Mini mags and let it rip.
Sorry guys----- I love my AWC's
Sealed suppressors are commonly cleaned by making a "tank" out of a capped off length of plastic sewer pipe and filling with a solvent. Depending on solvent and paint used, it might strip the paint off. Serial numbers are engraved in the metal, paint coverage would not affect the number.