Just J does it for me. Select one of the units you want to move, hit J, then click the destination. All units on that tile of that type will move towards the destination. It works rather like G, and you can even use it instead of G if you have a single unit to move.
Warning - if some of the units have already used up some of their movement then they'll get separated from the stack because they'll only go as far as they can. That can leave units exposed if you're not careful.
I've heard rumours that J and a modifier (shift? control? command?) allows you to move everything on a tile at once, but (a) I don't think I want to and (b) when I've tried is as an experiment it's never worked.