I purchased a can of Sawyer spray from a local sporting goods store and sprayed my pants, shirt, hat, and socks before a JMT thru-hike several years ago. There were misquitos on the hike and the treated clothes seemed to help, based on other hikers' experiences. I also use 100% DEET when the bugs really get thick, which, in my experience, is the only thing that actually works. The combination of the two allowed me to experience a relatively bug-free trip.
I'd use it again.