I would center a location on them and move them to it, so that they're stopped there. You could give them to another player on the move and return them once all the units run through the trigger. Complex, but effective.
As for hold position, it won't work so well, because if you tell a unit to attack rapidly(especially with Dragoons), then it'll fire, see that you're ordering, find out what you're telling it to do, realize it was alrady doing it, goes back to it, finds out you're giving another order, and so on