Hey chadol, whats up o/

FILD is a DEILD technique and you need to interrupt your REM (or close to it) to succeed
WBTB with FILD didn't worked for me, because every time I got too awake before got back to bed
I usualy prefer doing FILD right after woke
I don't think you can do it before bed, because to attain REM you need to pass per another four sleep stages
Well, never say never, so if you could do before bed it will categorize in a WILD technique

As a FILD user, I usualy set a calm alarm to ring after 3 hour of sleep, after turn it off I start the technique
this process works for me almost every time