Simple but effective for me:
1-2) mainline infantry
3) most important vehicle (anti tank gun if no important vehicle is on the field)
4) pioneers except for OKW, there it's my LeIgs if I have one
But I don't think there is a "general recipe" ofc. Some people don't want to or can't play with control groups. Or they are good at using a LOT control groups at same time but personally I feel like it would get out of hand and backfire if I would use 5+ control groups
