Many (and I mean many people) audio engineers, even the top dogs, don't actually have the correct technical knowledge into how sound works. Make sure the advice you get is scientifically accurate.
The only topic I've found extremely hard to find good information on is ambisonics. For specific plugins, read the manual and experiment/test. Look for generic stuff on compression, EQ, and not just for a specific plugin. You should be able to use Google to find other resources. (Masking, reason to use different sample rates and bit depths, synthesis (if you're using synths)). As will basic (or advanced as you want) knowledge of some DSP, acoustic physics, and psychoacoustic principles. Other than that a general compression/FIR/EQ knowledge/tutorial will do well.
Also, there is an official user guide for the ReaEffects