Good wool mittens with finger flap. Flip up to shoot and back down to stay warm.

For me what works the best is I use liner gloves on both hands with the warmest Mitt I can find over the top. Once on stand, I leave both gloves on my left hand and this is what I use to scan, etc. I keep my right hand in my pocket, with an electric hand warmer. I use the right hand to change sounds on my remote, as well as I pull it out when it is time to shoot. Most times, a long wait time would be 30 seconds - 60 seconds to pull the trigger. Even at -20, a hand with a glove liner can usually stand it for that long. As soon as the shooting is done, hand goes back in the pocket and I grab the warmer and a few seconds later, my hand is warm again. The electric warmers work way better than hothands, etc. Each one lasts about 3 hours, so I have 4 ready to go to last all night if necessary. Once the stand is over, I put my 2nd Mitt on for carrying everything back to the truck.

I used to carry a hand warming cuff when it got really cold. That works OK too, but just more stuff to take with you.