I use a detangle spray on Milly if I see some knots starting to form, usually under the armpits and across her chest when she's been wearing a harness.
They tend to make the hair more slippery and easier to comb out with less tugging. I've found that, by making the hair slippery, they can help in reducing the amount of snow that sticks to the legs and paws and also make any that does stick easier to remove.
I use Groomers Groom and Detangle Spray.
Bob.