the funny part is you cant buffer too early or you just get a 3A or 3B move. After 8 A+B B I start buffering when he lands, so its not that much of a slow buffer. and yes you can buffer during a JF twister for a second to come out, was practicing CH 33B, JF twister, JF twister and with the buffering is was coming out very easily but still working on it since I`m trying to find the sweet spot of when to buffer so I can get it each time.
As for the 1B JF, I highly recommend going with a muscle memory or finding a rhythm to it because if you try to do it by visual (especially after hitting 1B:B and going for another) it can mess you up since the enemy is falling during first JF. If you find a rhythm to it you can bust it out without looking and the hard 1B combo becomes a whole lot easier.
the 2143 B:B JF I just rely on muscle memory.
for agB, JF agB, 2A~BE 8 A+B B, JF twister/Twister
I use the same method for JF agB as I do for JF twister.....buffering. Surprisingly this one becomes easier although you still have to be fast as hell with it. For pad players, I bind L1 to A and as soon as I let go of A, I use my index and middle finger to do gB. I`ve gotten it to come out without buffering a few times but it does wonders when buffering.
1A

A, this one is very easy, you just have to know that this isnt a very fast JF, you have to be patient, once you hit the first JF, dont rush into the next hit. practice is the only thing I could add here.