I have the same problem. Here's what I've finally
come up with that works for me: first layer, riding gloves (currently
Ariats are my favorite); next layer: riding mittens
with hot packs in the finger areas.
Then when it warms up (we're talking PS winter rides
here), pull the mittens off and stuff them in the cantle pack, and you
still have riding gloves on.
I've also found it's really important not to let the
hands get cold in the first place (because defrosting takes a heater, and
is agonizing), so I'm really careful when I tack up too--ski gloves, with the
same hot packs in them, to make sure they're really warmed up for when I switch
them to the mittens!
Hope this helps any fellow RS sufferers out
there!
All these glove ideas are great unless you have a
circulatory disorder, like I do. I have Renaud's Syndrome and nothing
works to keep my hands warm in cold weather. Gloves are actually not
great at keeping hands warm for normal people. You isolate the fingers
and figures often do not produce enough heat to adequately warm themselves. If
you really want warmth, wear mittens. They need to be loos enough to
allow circulation but snug enough to trap the heat you
generate.