I don't have any suggestions for getting your diagonal right the first time, but you have a 50-50 chance of getting it right when you start posting. So you only have to look down once... if you look down and see you're wrong, sit for two bounces and post again. So it will be like: up down up down down up! If you do that correctly, you won't even have to look down and check. If you look down the first time and you're right, then just keep posting! Then you only have to look down again if you are doing sitting and 2pt also.
Every ride, good or bad, teaches you something new.