Wrist stretches/exercises?

Hello! new person here, been playing the shamisen (nagauta) for about six months now.
I was wondering if anybody had advice/suggestions on wrist stretches to do before or after practicing? After about 40 minutes my wrist starts getting pretty stiff and sore; in addition, I’m also an artist so I’m giving my wrist a lot of work on a daily basis. I’ve messed it up once in the past and trying to avoid that happening again…!
Was just curious if anyone had thoughts on this, any tips or advice is appreciated!