Grit??????

They naturally pick up small bits of sand and stone and such that serve as grit if they have access to it, whether it's a driveway or your yard.

When we first started taking our chicks out at a week old, we started offering them some grit mixed into their food as well, just to make sure they got what they needed to handle the seeds and bugs and not-as-readily-digestible foods they ate outside.  Once that bag of grit was gone, though, we stopped.  They handle it on their on and even pick up the sand in their run.

If it's just a little snow, they'll dig right through it.  If you're talking a LOT of snow, then I would.  You can just sprinkle it directly in the run or whatever area they typically roam in or mix a little bit in with their usual feed.  They'll know what to do.

If your chickens freerange or have a run that has a dirt floor then you shouldn't need grit. They will get what they need on their own. My girls are around 9mos old, they freerange maybe 6-8 hours a week (at this time of year, much longer in the nice weather) and they get plenty of grit, never a problem.

as an option to grit I save my egg shells and bake them then give them to the chickens they love them and its a great way to recycle the eggs and use all of the product.

You can just microwave them.  I do 2 minutes on high for 4-5 eggs and then grind them into powder in a a mortar and then mix it with their feed.  Keep in mind that this only works for a calcium supplement and is NOT a substitute for grit.