Once a day keeps it fresh in his mind while more often will probably just cause a lot of stress. In the AM (after a cool night) when the lights/heat first come on, and the snake is cool, is a good time. Just be consistent. Never put him back or down when he acts poorly, never reward him (putting him down) for musking you. Very shortly after he calms down, put him back and leave him alone the rest of the day. Remember you're trying to teach him that being calm and not musking will result in him being put back and left alone. It only took about two weeks of this to teach my babies. Now when I pick them up instead of squirming and musking, they just go limp and go with the flow. Adults seem to learn a bit faster, especially large females.