First get really comfortable hitting the jump.
Start by taking one hand off at a time, if you are finding this tricky then start by just releasing the grip with one of your hands, even just lifting one or two fingers off at a time will get you used to actually doing something while the bike is in the air as opposed to just hitting the lip and hanging on.
Once you can get both hands off one at a time and can do so comfortably then take a step back and start hitting the jump and just focusing on pinching the saddle between your legs when you are in the air.
Then start adding pinching the seat and taking one hand off into the same jump, making sure you are happy doing it with both hands.
Once you are happy with all that then its just a case of committing to trying it with both!
Remember to start small, just release you hand and lift it a few inches off the bars for the first attempts, getting them extended is just a case of lots and lots of practice, gradually throwing your hands out further.
Two other things to note:
1. Don’t start to remove any limbs or pinch the seat until you are at the peak of you trajectory, if you try to start any trick before the rear tyre has left the lip and you are in the air it will not end well.
2. When I was first trying them I was hitting the jump/drop with my braking fingers on the levers as I usually ride, once I tried hitting the jump with all digits gripping the bars it made it a a lot easier to both let go and get my hands back on. This might not help you or anyone else at all but it worked for me. Another advantage is that it helps you commit as you won’t be tempted to hit the brakes as much!
Like most things the biggest problem is getting your mind to play ball, you just need to commit!
Here is some inspiration for you, they are bloody good fun once you get them so persevere.