My two sets of liner glove plus over-mitt work for my occasional annoying Raynaud spasm in one finger and generally cold hands. Set#1 for ordinary cold weather has spandex liners with silicone palm and finger grips, and a not-very-windproof fleece overglove with fold-back thumbtip and four-finger mitten tip, held by small magnets. Bass Pro Shop, women's hunting clothing section, sold as set. On the men's side one can find flip-tip gloves and mittens, but not liner-plus-mitten sets. For seriously cold or cold-and-windy weather (like now, with minus 8 F actual temperature and winds of 5 to 15 mph), I use a thicker liner glove with silicone grip, plus a heavy nylon-shelled Thinsulate-lined double mitten with long adjustable cuffs. These nylon-shelled mittens need to be removed entirely, which is fine, because any flip-top mitten is inherently not too warm, and most of my time is spent getting to the location of the photograph, not in actual photography. This heavy-duty combo was found at REI, intended as snowsports gloves.
Clothing. Layers over layers over layers, with lots of zippers for venting. Base layer (aka long underwear) is ordinary synthetic runners' tights and extra-long sleeved turtleneck . Mid layers according to need: Down sweater. Additional down vest. Top layer: windproof waterproof long jacket, not insulated. Socks: merino wool, mid or heavy weight. Leg gaiters. Nylon windbreaker pants, mid or heavy weight. Beanie, extra ear cuffs, jacket hood. Neck gaiter.