So I'm sure this isn't for everyone... But on the me-stuff, I tend to both repeat and repeat until I can get it "right" in my mind, as well as play around with it. Trigger myself on purpose, until I can figure out all the natural boundaries, and then start messing with them. Coming at them from the side. Or work myself right up to the boundary, until I've pushed the boundary further away, or just say screw the boundary.
There are a lot of things that I can't do that with, and with those, I have to find work-arounds. But oral sex and breath control and gag reflex stuff were things I could play with, so I did. From things like giving my mouth a whole lot of sensory experiences (including talking with my mouth full, or around ice, and under water, singing ditto, and -oddly- walking was hard -even though I've been walking and eating for ages. When I found that out I refused to eat sitting for a few weeks, and started carrying lolly pops and sunflower seeds to really trip my brain out... Along with different food textures) to training my throat to swallow from thick liquids, to pills, to whole grapes, etc. I actually looked at how drug mules train themselves to swallow balloons. I brushed my teeth & tongue with a washcloth (that actually works better than with a brush, oddly). I used chloreseptic (mild topical anesthetic spray) when necessary. And I did a whole lot of breath control. I'm a swimmer, and one of the primary rules of swimming is that if you can talk? You can breathe. (This is actually something. I've always used in panic attacks). From gargling to "gulping fishes" (that mixed air and water choking feeling). Lastly, I went on a fellatio mission. Learnt everything I could about it. Including how & when to breathe through my nose. Talk about a lightbulb moment! Shazaam. That was eye opening. Like I said... I'm sure it's not for everybody. But it's what I did.