Russell, good luck with the tasmanina cutback! It's a difficult technique in my opinion, but I'm sure you'll get the hang of it!
One of the mistakes that I made while trying to learn the tasmanian cutback was that I didn't wait long enough before changing directions. Warming up befrore going for a session is also helpful in order to prevent injuries on your shoulders/wrists.
You could also start by brining up the whip against the curve, so you can bring it down with the curve without having to do a rotation. Once you feel cofortable doing that you could add the swivel (bringing the whip up with the curve, swivel, and bringing it down with the curve again).
All the best