David, it sounds like you'e got this figured out. I have found that if I draw a little picture showing the diagonals I don't even need to write down the treadling....just follow the picture and you can change up your treadling easily for alternate twills.
If the line is going up hill for a 2/2 twill it's 12, 23, 34. 14
If it's going downhill it's 14, 34, 23, 12
If it's at a point, you don't treadle the pick twice...eg 12,23,34,14,34,23,12
I'm attaching a little photo with examples: