Probably the best advise for good bottom turns is to go out and do a couple of hundred then see if you still have the same issues. Like a hypochondriac by the time you have sorted out one issue you may well have developed a bunch of new issues that are also apparently just as complex. This is why I think the best wavesailors are the ones that don't think to much about things they just go out there and try to smash the waves and sometimes smash themselves a bit in the process.
I remember watching a young Josh Angulo sailing Margerets main break and absolutely launching himself into the biggest sections and destroying at least two sets of gear but somehow walking away without injuring himself. There were lessons there to be learned but not by me, I stayed wide and on the shoulder unlike my fellow Tassi sailors who both went deep and scored some great waves but also had big swims across the reef.
I think a valuable lesson for any GPS racer is that the surf zone is no place for navigation by GPS. The photo below is of an unnamed sailor who had checked his GPS and convinced he was out in the channel decided that it was time to gybe!!!.
Such GPS based navigational errors are apparently quite common with sailors leaving one beach and returning to an entirely different beach entirely by accident. (This sometimes happens to my mum when she goes to the shops but as she doesn't carry a GPS I think it's entirely understandable.)
Gear choice can also be a great source of angst for any aspiring wavesailor it's a commonly help superstition that you should never ever wavesail on a green board and that you should only use 20'' harness lines or 28'' but never ever use 24''s.
My own recipe for happy wavesailing is only ever to sail small waves and only ever sail in cross onshore conditions and always sail a red board no matter how many fins it has. The front hand on the boom should always face upwards (except when it is facing downwards) and the back hand should always extend towards the back of the boom at the start of the bottom turn.