I did the HAST last year for entry into Penrith, and I got in. Basically I started preparing by using this HAST practice on NotesEdu, it's like $150 for a test pack, but this basically only helped me for the Abstract Reasoning, the other stuff wasn't really relevant. The HAST is really similar to the new selective tests that Department does, so if you can find the tests after 2021, and get familiar with those, they really help. I also practiced my writing a lot, my question for the writing test was discursive, so if you don't know that already I'd suggest get familiar with it and strong at using it as it may come up. I think Matrix Education also has some useful information on their website so you can check that out too. Good luck!