stop making it harder for yourself.
if you can’t do the mount how one person does it… don’t dwell on it. find the way YOU can do it. I’m on a 20" and i basically do a 5/11 o’clock pedal position. put all my weight on the bottom pedal and get on up. this is opposite of how most people seem to say which is - pedals at 3 and 9 and put no pressure on the pedals and float onto the seat. the way i do it seems to be the ‘old school’ way, but it’s what works for me.
just start out with the pedals vertical. put all your weight on the bottom pedal and try to ‘lean’ yourself up onto the uni. if you try a few times and you don’t seem to be able to, or feel comfortable, pushing off the ground enough to get vertical then adjust the pedal positions slightly so that the bottom wheel is now a little closer and more at 5 o’clock. this will make the wheel roll back a little and help get it under you. keep playing with it until you get a comfy combo of enough rollback + enough pushing-off the ground with your grounded foot.
don’t even worry about putting the second foot on the other pedal. for a little bit just try to keep getting up over the uni and then let yourself ‘fall’ back to the ground. the idea being that you are trying to get a feel for REALLY being balanced above the uni and getting that part spot-on. it’s a lot like trying to balance on a pin-head, and the smallest error will stuff it all up and have you falling over instead of balancing on top.
BUT, it might pay to have some music or something in the background to slightly distract you. the more you focus on nailing your balance PERFECTLY the more likely you will fail, because unicycle reality is that you will never ever be perfectly balanced and every moment on a uni is a moment of ‘damage control’ in trying to keep the uni under you while gravity keeps trying to knock you off it. once you get SOME kind of balance then that’s all you need to get going.
!!! you AIM for perfect balance, but you ACCEPT what you get !!!
once that’s covered and you have a good feel for being fairly balanced after leaving the ground you can then start getting used to putting your other foot on the other pedal. after that you just then need to get used to sitting FULLY in the seat. after that you just need to rock the pedals a little in a mini-idle to get yourself leaning forward and away you go.
do this away from everything. no aids. no walls / cars / friends hands. if you have an area you can ride in then keep trying to mount to then ride. if you can’t mount you don’t ride. at some point you will start nailing the mount more often and can then ride for a bit until you dismount.
if you get this far you have won. you have proved that you can mount and then ride unaided, and are more well-rounded than some people who have been riding for years who still can’t mount unaided.
and if none of this suits you then don’t bother with it and try something else that does work for you.
yeah just don’t. try what i said above. if you are trying to sit on the uni while grabbing something else then the uni will at some point probably twist and squirm away from under you if you are slightly off from vertical. the more you try to grab the aid and stop from falling the worse it seems to squirm. it’s just how it is. if you hold something at arms-length and the uni starts to squirm away from you then there’s no way you can push away from your support any further to try to compensate so the wheel just keeps squirming further and further away until dismount.