Hey Guys,
Two options that I have found work really well.
1. Cork deck grip bought or made out of cork tiles, downside a bit heavy but don't suck water and the grppiest grip I have felt. If you can find thin cork such as a wall covering that is around 1.5 to 2mm thick let me know - i would cover the entire deck as the stuff works so well.
2. Get some spray-on grip like what the SUP's use, apply, let dry and then wax it - wax goes down well and stays put and if the wax wears out the spray-on grip is still there as a backup. The downside is that you may not be able to paddle surf it as it may chew up your chest / wettie or whatever.
Cheers
Rich