Specially for this “apparently” similar radicals or the Kanji derived from them watching them in different fonts will help a lot.
First WRITE them, even once, so you see the traces that make them.
Something like this script will help at seen them in different fonts right here on WK
In my case, I do the same, but in Anki.
And you can see how apparently very similar Kanji difering only in those radicals you mention, when writen in different fonts the differences are way clearer. This will become even more evident if you write them too, since you’ll be much more aware of the differences.
Here is 穴 and 六 … “similar” in this tiny view, and with the generic font.
Now different examples (focus specially in the bottom right fonts, since those tend to be much more bare bones an are a better example of what traces are considered important to identify the kanji even when simplified)
See how different they are?