thats the easiest step of the method besides brute force alg memorization & execution for COLL. what exactly don't you understand?
i made a short list of the algs for the possible combinations which can occur. i can send it to you if you want, but i don't think it'll help you at all.
step 4a is quite intuitive, once you take the time to make yourself a training cube for step 4. do this by taking a cube without stickers on it and place 6 stickers on it, representing the 6 remaining edges in an disoriented stage (the stickers should be at the following positions: FU, LU, BU, RU, FD and BD) now with only using U/U' and M/M' turns try to flip the edges. thats how i learned it.
by now the whole step 4 takes me between 7-15 seconds (worst case, 6 edges incorrectly flipped and the 'dot case').
Gilles Roux says "Using this rather intuitive technique (...), you can solve the last 6 edges and 4 centers in less than 5 seconds on average (...)."
i average about 45 seconds, where the last 5-7 seconds are step 4 (yeah, I still suck at block building (step 1&2)
)
just watch
Richard's Videos with a cube (preferably the 'training cube' for step 4) in your hand, look what he does, use the pause button a lot, think about what he says, try to set up the cases he's showing you (you can see what he does to set up a specific case) and finally repeat till you understood it.
