So I thought this was fairly common knowledge, but after seeing many scenes of folks getting pushed while stuck in the snow, including a Jeep with snow tires spinning the left rear and right front tires, it evidently is not "common".
All you need to do is drag the brakes slightly and without going into the technicalities, it will cause torque to transfer through both (or all four) wheels even with an open differential. Used this technique to get moving in mud or snow many times.

 

insall a spool, weld spider gears or install lockers

 

Thanks for the tip. Common sense I guess, but it never occurred to me.

 

i could have used that today while getting stuck in my rwd pickup. ended up having a farmer and his son push me out.

 

Yeah, and for rwd only it works best if you just apply the parking brake slightly so you don't have the front brakes fighting you.