I probably can't be that helpful as I struggle with combos too, like the double JF twister and 1B:B combos, but I'll try to give some advice...
The main thing is to spend desperate hours in training :P
For the twister, start by practising 3aB from crouch to get used to the slide input. Once you're fine with that, start using 2143aB over and over again until it's just second nature. If it's the directional input you struggle with, 2143B might be worth practising first. Once you get the twister into your muscle memory, using it in combos shouldn't be a problem, especially with the buffering.
