I just get under the shower in it to wash it outside then take it off and rinse it inside.
This is good for many sessions, every once in a while if it smells a bit I'll wash it with the same shower soap i use on the rest of me.
I try to avoid pissing in my wettie, I don't really want to wear a wet suit full of piss for hours and if you do even once this will get it stinking in no time obviously but sometimes you just gotta go, you can also land your kite and go behind a bush, (when are they gonna invent wetsuits with flies??), or in a shorty you can stick yer dick down one leg and relieve yourself that way, while in the water perhaps and not while jumping. Actualy it's a bad idea to piss in your wetsuit in cold weather because although it feels warm, you're actually losing body heat to the water, it's warm liquid leaving your body.
One thing that can stink a lot is booties, I find that a weak solution of bleach/soap when they smell will kill all the bacteria producing the smell, don't leave it in the boot for more than the time it takes to slosh it around rinse it out, wash it out several times. This will probably shorten the life of the rubber/neoprene a bit btw and I wouldn't do it with a wettie but it stops the ladies avoiding you like the plague, unless they have another reason for doing that of course.