do u mean normal db->f  then follow up by ultra (db,f,b,f+ppp)?
if yes, its easy la.

first, db->f+p then quickly do a b,f+ppp. the second time no need to charge.

no need to rush lar ryu srk to ultra, can count 1 2 3 and do step by step.
doing it too fast will only screw it up, either ex srk come out or whatever.

trust me lar ppl, once you get the FADC down, you can just execute the metsu hadouken casually.
it's probably one of the easiest juggle in the game.
landing the srk is the harder part.