As mentioned in your other thread, there's a lot of ways to approaching it that will produce different looks.
If you're trying to follow that video tutorial, spend some time also looking at glazing tutorials, as there's overlap between what you're looking at and just traditional glazing. As you already figured out, you need to learn how to "sweep" the paint so that you end up with more in the middle of the membrane than near the parts where you want it darker, then build that effect up over multiple coats allowing them to dry in between so you're not removing the paint from the previous coat.
In terms of the paint drying too fast, maybe your house is too hot and too dry. In my house, if I try painting on a summer's day the paint dries almost instantly, whereas in winter I can work it a lot more. OR, maybe you're just not working fast enough. You can add drying retarders to the paint to slow the drying and give yourself more time to work, which can be useful for some techniques.
If you want to branch out into other techniques, I mentioned in the other thread the idea of drybrushing / stippling, or you can try wet blending, or you can try oil paints. Just search on Youtube for "wet blending miniatures" or "oil paints miniatures". Marco Frisoni has some guides on oil painting miniatures, like this one:
https://www.youtube.com/watch?v=x_pxojd7kp8
I'm not saying you should use oil paints, I simply throw it in the ring as an option that you can consider along with other techniques.
I think the drybrushing / stippling approach (I linked a video in your other thread) is probably the easiest way for a beginner to get some nice colour transition effects. But all methods you need to learn, the best way to learn is to have someone guide you face to face, the next best thing is probably to watch videos where they show the whole process start to finish (not just doing a couple of sloppy coats then cutting to a beautiful final product!).