Yep, by 4 yrs I would be taking the same path as you. Firm, kind but consistent....is he at 4 yr old Kinder, I think once he gets the hang of this everyone's life will be easier, yours and his and if he is at some kind of day care/kinder, the carers as well. Good luck. Lots of praise, maybe a reward chart, try not to back down, it will be a challenging week but well worth it when he has got the hang of it. x