@SirNuke The other reason to not use steel wool is that it can be a fire hazard. A low voltage shorted across steel wool will result in fire (I carry a 9-volt and steel wool in my camping kit as emergency fire-starter).

@SirNuke Another option if you don’t want to source excluder mesh is to get some “backer rod” - a painter’s product sold as “caulk saver” at the home improvement palace. You use it to fill large gaps which you then seal over with caulk or silicone.