clean the ID of the housing recess to aid fitment & if that seal has the spring on the back side, pack that recess with vaseline to help hold it in place. it is a good idea to grab a helper to hold it and the pipe (get a piece of pipe with a wall thickness wide enough to cover the seal width). critical is the first few blows to get it started straight. You likely need to sand the ID slightly to remove burrs and clean the paint off of the seal OD (every bit helps) as it sounds like there might be a few tho too much interference. As you know don't let the debris from any sanding/polishing end up where it ain't supposed to.