Unless I am misunderstanding you, you clean the dust and junk out of the shot before you try and load it. Reclaimed needs to be screened first to capture oversize shot and debris. Then a magnet should be run through it to get out any steel that might be in the mix. You can add graphite to it and run it through a brass polisher, something to agitate the mix. Don't have to add much; a little graphite goes a long way.