How to do standing-up changes, Ok well this is how I generally do it for poos.
Firstly she has to go (or be carried) into the bathroom, though I don't always bother if it's just a wee. If she is happy I just get on with it while she stands there (chatting or whatever) but if she seems inclined to wriggle or run off, I get everything to hand (including opening the nappy bag, unfolding new nappy etc), kneel down and then wrap my left arm round her middle so my hand is behind her back, and then use that hand to hold her dress/top up out of the way. It also stops her running off, and stops her being able to sit down easily halfway through, as I can hold her up under her arms if necessary.
Right hand pulls down trousers, then I undo the nappy tabs with whichever hand can reach best, but while supporting the nappy so it doesn't just plop straight onto the floor. Then the trick is rather than just pulling off the nappy, to kind of grab the poo with the nappy as you pull it off, so you can remove the maximum amount of poo at the same time. Plonk nappy on floor, but keeping it closed so the poo doesn't get on the floor (getting it into a bag one-handed is too fiddly!), one-handed bum-wiping like crazy until clean (just reach underneath for the front bits), put the new nappy on (I usually shove the front bit up through her legs from behind first, then pull up the back bit and do the tabs) - pull up trousers, release DD and clear up the dirty nappy etc. and Bob's your uncle!
2 other good tips I have learnt: Firstly, if it's a bad poo, do it near the toilet and for the first bit of wiping, just use loo roll and then you can chuck it straight in the loo as you go. Much less fiddly than having to get it in a bag, and you can still use wipes for the last bit to get really clean.
Also, for DD it works really well to put a book or a toy on a chair in the bathroom (or edge of the bath or whatever you've got available). Then she plays with that while standing in front of the chair and I can change her in peace.
Bit of an essay but hope that helps!