We don't know yet if there was a homemade silencer/suppressor, or more than one, or even if what was found belonged to Billy - just that something like that was found in a well October 30, 2018, possibly constructed from part of a Maglite.
An article published June 10, 2018 mentioned a conversation at a derby: "In between engine roars and the crunch of metal, Joe, who works as a mechanist, said investigators actually paid him a visit. They’d heard he’d helped a friend make some silencers, which he had, and which his friend is legally registered to do."
Eight unsolved murders in Pike County, Ohio
IMO, that means LE was already investigating the possibility of a silencer/suppressor used in the murders; probably because 'fluff' from packing fibers were found at the crime scenes, and likely in the close-range wounds.