I wet my itomaki but it didn’t seems to be enough… I also tried Kyle’s trick: scrape some rosin with a knife and put it with a Q-tips in the hole and on the tip of the itomaki.
Now I can at least play a few minutes in a row before having to tune my shamisen again. The itomakis stays in their hole much more longer.
Just can’t wait for spring to come! Opening the window and welcoming fresh air and a little more humidity will help a lot I hope.