IMO it all depends on what part of the season you are hunting. The first split I will set up up to 4 dozen full bodies. When I have that many decoys out I find its a little better if there is maybe one or two guys clucking and one guy on the call. By the end of the season when when I am setting out 3 to 5 decoys there's only one person calling. As far as what to blow at them its a three note yodel until I get their attention. Once they are interested I lock in on the loudest bird in the flock and just respond to his call trying to mimic what he is calling. You just need to convince one of them to come in usually. When I get more than one flock working I shut up until they settle down a little then I just start clucking softly.
There's a guy down the road from me that has a guide service. He sets out 4000 rags and 500 full bodies every morning. He usually has 4 or 5 guides and 8 to 10 hunters in the middle of the spread. All of his guides do is cluck and he is the only one calling.
The most important thing in my opinion is establishing a dialogue with one bird and convincing him. It takes the guess work out of it.
Callling is the easy part, its all the other stuff that flares the birds. Improper decoy layout, keeping everyone in the blind still and not looking at the birds, staying hidden yourself and not echoing the call in the blind, shooting too early are the things it takes a while to get the hang off. They always look so much closer when you are crouched down in the ground.
When you say "not echoing the call in the blind" do you mean from calling down in a pit? I'm assuming it's best to point the call at the birds over the top of a blind if possible? And yea the few times I have shot specks, if I were calling the shots I would have jumped early every time. lol