If it helps.. I first learned the manual feel by trying to manual through a set of small double rollers. That is how I taught my kids to manual.
As you approach the roller dub, get your stance and pedal position set and try rolling off the roller face and keep the front wheel up until it smashes in to the second roller. Keep doing that until you progress the front wheel over to the backside of the second roller. You will also notice as the rear wheel crests the peak of the first roller and down the backside, your rear wheel and feet will drop and your hands and handle bars will come back closer to your chest - careful as this is where you could loop out. If you feel like you’ve gone to far, (it will happen fast AF) quickly grab brake or bail or risk landing on your ass / back.
However - looping is a necessary evil as you will learn the limits and balance point. You could mitigate loop out / back smash risk by learning to step back, put a foot down and catch yourself when you loop. You can simulate that in the grass. Pull a wheelie too far and put a foot back and down behind toj and catch yourself. Get used to that and as you practice manualling, if you feel the loop out coming, you’ll be comfortable catching yourself.
good luck - post up a progression video and let is critique it.
if any of this sounds scary and something above your risk acceptance level, don’t do it.
lastly - the key to shredding on a bike is to stay loose, relaxed and nimble and not tense, stessed or anxious. The latter usually results in injury.