I just slide them down like a pullup. Now with so many premium ABDL and medical style diapers available with the hook and loop system it is much easier. You can even loosen you diaper all the way if you want. Diapers like Rearz happy quality enough tapes that you can usually get away with atleast to refastens which is almost always more than enough for me before I change into a new diaper.
Generally, I stand up, carefully slide my diaper up, and then refasten/adjust the tapes. The tricky times are when you rush to get your diaper up because you are in a crowded restroom. Sometimes that can lead to ripping or that your diaper just does not get pulled up all the way. It also sucks when you are sweaty.