I use speed 4 for applying waxes and 4-4.5 for some one-steps like
AIO. Mike Phillips sometimes uses even slower speeds with products like
NXT when he's working on delicate finishes. An old Allard he did for auction-prep (green single stage), comes to mind; IIRC he used speeds like 2 and 3 on it as he didn't want to risk any damage at all.