Remember the J stroke you used to keep your canoe going straight while summering at Camp Kookooraruu? You’d think it would have some similar utility in the SUP world. But for most people it really doesn’t. I’ve tried it, to no avail. And so has Gorgo, over on the Seabreeze OZ forum, Seabreeze Forums, who states his opinion on the matter with no ifs, ands, or buts:
The short answer is that it is unnecessary and horribly inefficient.
You can make a J stroke work and force your board to track straight but you will waste a heap of power and feel like a dork doing it.
The reality is some boards track straight and some don’t. 
If your basic stroke is solid and your board is still very squirrelly then you have two choices:
- work with it by starting your run for a wave in a side-on position and only digging in hard late with a paddle swap if necessary.
- get a bigger fin (a much better solution for flat water or surfing at trim).
If you watch a heap of videos and do a heap of paddling you will notice that nobody does anything tricky or special when paddling other than keep their arms straight during the power delivery. No "chicken-winging" allowed.