Instead of memorising these algs as separate cases I memorised them as a sequence of transformations from some "base" algs.3. Some of the are easy to understand (for example commutators), but some others are hard to understand. There are many 2e2e cycles that I don't understand and I have just memorized (for example F2 L2 U R2 B2 L2 D R2), but sometimes I forget them
I hope someone else has a better answer for this.
Here's an example, take this 3e alg:
R2 F2 L2 U B2 L2 F2 D
We can get another alg for the same case by doing:
R2 F2 L2 Uw B2 L2 F2 Dw
We can generate a 2e2e alg from here by doing:
R2 F2 L2 (U y2) B2 L2 F2 (D y2)
From here we can generate more algs by cyclic shifting (moving moves from the front to the end)
F2 L2 (U y2) B2 L2 F2 (D y2) R2
L2 (U y2) B2 L2 F2 (D y2) R2 F2
Of course after using these algs for a while I've gradually learnt how to do them directly instead of going through the transformation process, but it helped with learning.