This is definitely the most clunky part of DK1 but yes, Call to Arms is your best tool. You can power it up by holding down the mouse button when you drop it. It costs more but has a larger radius.
You can use the barracks to group up creatures, drop them in there, use the possession spell on one of them and the rest are supposed to follow you as you move about in first person. Dubious usefulness against the AI since they will just drop all their minions on you once you’re on their land.
Guard rooms do work, but they have to be a certain size and creatures will take breaks to sleep / eat / collect pay. Rarely use them but must be placed in a choke point to have any effect imo.
