Honestly, I don’t think there’s really an answer to this resource question, as I think it’s pretty personal. After all, no one else can cram information into our brains for us. So it has to be us finding a way to do that for ourselves, and what’s memorable to one person is forgettable to another. So I just go one by one and work at it until I find something that sticks.
Your example is a really good one for a lot of reasons:
体
休
While I agree that it’s helpful to see these “in the wild”, recognizing that one is “body” and one is “rest” in the context of everyday usage doesn’t necessarily mean we really know them (there will usually be “clues” surrounding them: I can recognize a common word in one place, yet not recognize one of the same kanji in another); and, I’d argue that, for the purposes of learning kanji in general, deep-diving on these and others that are visually similar at a glance will pay off in the long run.
My approach would be something like this (at this point – your mileage may vary):
体 = 人 + 本
Just on its face, a person and book suggests something tangible, which may be memorable enough. But In Japanese, I see and hear this word a lot:
本人 (ほんにん)
That’s something like “the person themselves”, which even more directly suggests…a body.
On the other hand, there’s a significant difference here:
休 = 人 + 木
Rather than a book there’s a tree with the person. Personally, I imagine someone leaning against a tree to rest in its shade.
Now, you may be thinking all of this sounds like a lot of time and effort (and long-winded explanation!) to differentiate between two kanji, but…that’s actually kind of the point: you’re much less likely to forget after this, because your brain is repeatedly being exposed to more varied information about it. Also, paying attention to the tiny difference in this case will apply to many others as well.
WaniKani is great, and you’ll likely find that for some kanji, seeing them over and over is enough for your brain to remember them. But increasingly the differences will be more subtle, so it’s helpful (and perhaps critical) to slow down on ones you’re having trouble with to soak up more information. WaniKani has great example sentences and other detail for each item already, but other resources may help with particularly un-sticky kanji. I hope this helps!