Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
I never had problems clipping my backpack with harness on me at same time. During alpine climbing or XC skiing I actually always have my harness on me. It just takes to long to put it on and off each time you need it. And not clipping waistband of backpack makes it very wobbly and unstable.
T-shirts are made not only from the cotton. Wool ones are nice to keep the smell at the minimum. Usually I take just one for no matter how long trek and wash it in the streams and lakes. Synthetic are nice as well. The ones designed for runners are particularly good in hot weather.
If you go with boiling. And usually it's the best and cheapest solution, you need to boil it for 20 minutes to kill all possible bacteria and viruses. That is a common way of sterilizing bones in veterinary academy.
Dry shower works fine for 1 - 2 weeks expeditions on altitude. But it's personal. Some folks need 2 showers a day, others get away for weeks without one.