Whose in charge ?
I suspect you wouldn't let him take a crap in your front room while guests are over.In the same you don't need to let him control you with this.
Let him pick out a type of brush and or paste, but his control stops there. Sit with him doing it until you are happy with the job. If he stops too soon or doesn't do it right make him start over. It is worth the effort and not abusive.