No guide, but i sugfest experimenting.
Most layer operations you need are straight up adsitions and subtractions.
Yes, they can get crazy complex in term of sequence, but it all essentially boila down to an easy to visualize White/Black twxture that can be directly output into the base color for development purposes.
Just pay attention to what you do;
Base layer > subtract grass Layer
Is likely the same as inverting the grass layer.
Then again the cost is arguably similar between the two options.
Anyway, you can easily prototype the math needed to power basic lerps, which is kind of the point there.
And you can also learn more about materials, since you will no dobt end up doing more complex things…