mtbdarby- you can try taking a damp washcloth to his face (cheeks where they like to rub things) then go rub that on the spots he's marking so they already smell like him. I can't remember how frequently you have to do it- every couple days or everyday til he really gets that there's no need to mark. I think I saw it on the British show Barking Mad that's on Animal Planet and maybe a few other similar shows