There are 9 main academic tests on the WJ. Think of it as a 3x3 matrix. Reading, Writing, Math, crossed with Skill, Fluency, Application.
The "Broad" clusters use all three in a domain, and Broad Achievement uses all nine. The "Brief" clusters use Skill and Application, leaving out Fluency.
You can also get clusters that look at Skills, Fluency, Applications across the three domains.
I would not use the grade-equivalent easy-to-difficult information to guide instruction per se. I might use those to make arguments about how bad the mismatch is for a given kid in a given classroom (when making a case for GT interventions or for an IEP). Frankly, as a homeschooler, what I usually suggest is that you look at actual skills in the various domains -- if a kid can do a skill easily and smoothly and correctly, then ramp up the difficulty a notch until it takes them some effort, and instruct there until that gets easy. You have the luxury of tailoring things to the kid. When I write reports, I do try to make notations of specific types of skills the kid could and couldn't do, to give a sense of where to start.
