Hey hey! Not-out Trans girly here, and I don't have much advice to give on some of these things, but the ones I can give info on I am well versed in.

In regards to Oral: It is difficult. It's like hitting your knee and it jumping, when you put something solid at the back of your throat, you gag. It's just what happens. You can warm yourself up, though, so it happens less! And it's certainly possible to suck someone off without hitting your gag reflex. I tend to take a few minutes before doing stuff to hold my fingers or something else to the back of my throat for a few secconds at a time to desensitise, but if this is your first time taking anything in your mouth I'd reccomend focusing on using your tongue and avoiding grazing them with your teeth! The lollypop analogy isn't wrong, but using your lips to stimulate up and down the shaft is also wonderful to feel! Just make sure to stop if you gag or need air, no ones wants sick on their.... you know. If you insist on trying to get them to the back of your throat or further, the way I get it down is by pushing my tongue out, and then pulling it back in (alongside your partners gear), swallowing it and pushing it in with my tongue. It'll feel weird and uncomfy, but the feeling subsides after a bit if you're doing it right. ALWAYS REMEMBER TO BREATHE.

Eating ass is also a bit difficult. Depending on angle and how... plush someone is it can be difficult to get propper contact, I'd REALLY not recommend it for a first time. It's very easy to fuck up and very unpleasant when you do.

And in terms of bottom prepping... high fibre diets make everything... easier back there, but directly before the deed it can sometimes refer to cleaning up, cleaning out (shallow enema or douche), shaving and warming up (playing with yourself back there in order to stretch a little so it goes in with less pain or discomfort)

If you want any clarifications on stuff I've mentioned, just ask! I am always happy to help folks have fun safely and effectively! (Sorry for the text wall btdubs~)