It *can* be done standing up, but you have to be all the way to the end of the tube and lined up properly. Using a silicone lubricant inside the tube will help prevent getting 'stuck' and a Q-Tip/cotton swab (or similar tool) will help with alignment issues. Don't use the little, hollow plastic coffee stirrers you sometimes get with take-out coffee, the plastic can be sharp

ouch!
Sometimes it can be easier to use a sink instead. Yes, some folks might think it odd, but the sink drain goes to the same place as the toilet drain, the only difference is in peoples' minds. Don't get caught doing it, they will think you are strange...
If you are not all the way to the end of the tube, pulling the scrotum through and pushing the assembly tight against your body may help. If you regularly find that you can't be all the way to the end of the tube, you may need a smaller/shorter tube (6000S).
One or two squares of toilet paper, folded a couple of times, helps to mop up the little drips at the end. Since it isn't possible to squeeze out the left-over, there will always be a drip or two that comes out later. Don't wear the same undies every day (nobody needs to be told that, right?).
02/11/18 "The idea of me fucking someone else really turns you on, doesn't it?" --Mrs. Twisted