I am not a technician but live in MN and do a lot of outdoor stuff in the winter that requires finger dexterity -- keeping warm and being able to good finger control is one of the toughest things I have tried to solve.
First, one of the big difference-makers is your overall body temp. Hands tend to be less of a problem if your trunk/arms/legs/feet are warm. So, your other question about heated clothing is an important consideration. I use either multiple layers of fleece or when I need an extra boost, use my Milwaukee M12 heated jacket -- works great and isn't bulky.
I am a huge believer in foot/hand warmers. They're expensive when you buy them in single packs but pretty cheap if you buy a box full at places like Costco (I think they're like $13 for about 50). When I need to use finer tools outside I use unlined deerskin gloves which give a good grip and, next to kidskin, are about as close as you can come to bare hands (for leather gloves). If the gloves aren't enough on their own, I put hand warmers inside the gloves -but- position them on the back of my hands (not in my palms). This gets heat to the fingers without having the bulk of the warmer "pack" in the way. For the times I have to take off my gloves and use bare hands, it is nice to have the gloves laying nearby (with the warmers in them) because when I put them back on it's like instant warmth.
Good luck to you!
Big K