The difference is, in mixed escape, there is usually a primary escape, then just sometimes you’ll have a note here and there that doesn’t “work”. So you just use some type of helper motion to pick it. DBX is just all down strokes escape and all upstrokes escape. So for DBX you need a very specific type of motion that will accomplish it.
I’ve had this technique as a little “project” I’ve worked on the last 1.5 years. I was able to get the core motion within a week and I detailed some things about it here:
I also recently put up tabs for a blugrass tune that’s almost exclusively DBX
Those might help give you some variety.
I think the main thing is to “find” the motion. If anything is not working, don’t keep doing it hoping it will fix itself. Spend that time changing variables until you get something that definitely works. For example, at the 0:34 mark in the slo mo video you just uploaded, you had a clean set of string changes. See if you can replicate that. Not sure if it matters but you did that by going “U D U” on the B and high e. Also around :40 you got clean escapes on G B E B, going “D U D U”. See if you can replicate that in isolation too. The first thing I found I could do was 3 ascending notes (1 note per string). Then I could use that to get 4 ascending notes. Then I started working on descending. I just tried playing as fast as I could with a variety of grips/anchors etc till something started working. Once you get something that’s working, you have to do more and more of that and see if you can associate the feeling of that with what you’re doing to cause it.
In general to me, it looks like the issue is that most of the upstrokes are not escaping, and that is common for folks who have a more “DSX” trajectory.