Experiment with several mini-mashes. That's what I did when I first starting using rice. I didn't want to commit all of the money, time, and materials to a large batch until I was convinced the process was at least sound. Once I had some confidence that I was on the right track, I went ahead with a full mash. I'm still tweaking things, but I'm getting good results and haven't made too many of those "big" mistakes.

Try a few mini-mashes that only produce a couple of liters of wort, take good measurements and keep good notes on proportions, temps, rest times, etc. etc.. Then try fermenting ... you can use inexpensive baker's yeast since it's all just testing anyway. If you can get a reasonable OG and acceptable FG, then you'll know you're in the ballpark and it's time to scale up.

opening specific gravity and final specific gravity