I’ve had the same problem. Here’s what worked for me.
I assume you can do the shoryu FADC without much trouble. The way I trained myself is instead of doing the ultra I would just do a single hadouken while looking at my hands (I’ts easier to move your hands where you want them to when you’re looking at them). The moment that feels natural add the second motion and perform the ultra. Just do it as slow as possible. Once that feels natural speed it up a bit. Again while doing these keep looking at your hands. After a while you will probably start landing the ultra. Once you start landing it try and remember how it feels like. At this point i would just quit and continue the next day rushing it wont help.
Day2:Just do everything again listed above. Once you nail these again consistently perform the steps listed above without looking at your hands. And here’s where the feeling part comes in, just try and recreate the feeling (Don’t think. Feel!) .
Also if you’re having trouble just doing the ultra you could also practice with Dhalsim ultra 1. Push them in the corner and just keep doing the ultra.
And about your technique, I use the same hold. But on P1 side I use my wrist alot more than on P2. I would just try using my wrist or maybe even a bit of your arm and see what is most comfortable or reliable for you.
This worked for me hopefully the same will happen for you.