I do a quick rinse nearly every night and sometimes during the day when an opportunity presents itself. As Roger mentioned, it can be a very quick dip followed by an equally quick exit. I call it the high mountain dive, it’s where you dive off a rock and turn towards the shore before you hit the water, effectively cutting your exit time. In streams, rivers, and small ponds where there isn’t enough water depth to dive, I wade in and then lie back. I then use a couple of drops of Dr Bonner’s under my arms and in the nether regions away from water and rinse with a few squirts of my water bottle, which double as the back country body bidet.
I also rinse my hiking clothes out nearly nightly and find they are pretty much dry in the morning, although I must admit there have been more than a few times I had to beat them on a rock or log to loosen up the ice. It makes for an invigorating first mile or two but when in cold temps and wet weather I will typically refrain from the clothes rinsing until better weather.
I sleep in my “camp” clothes which consist of Patagonia lightweight long tops and bottoms and a clean pair of light socks. Just over 8 oz for a large top, medium bottom, and liner socks. I know, this is BPL but I sleep so much better and they also are my cold weather base layers if the need should arise.
I cover up in the sun and hike in an OR sun runner hat with cape and long sleeve mock t and use sunscreen only on my hands, if at all. I hike in long baggy shorts and between those and pulling my socks up, I am pretty much covered. Pun intended.
As to underwear, I hike in nylon mesh boxers that get rinsed out nightly and will dry very quickly, even in high humidity and cold temps. There, perhaps a bit too much info, but this has worked for more than 45 years of backpacking and thousands upon thousands of miles in all kinds of conditions, at least for me and as always, YMMV.