Something that I have found that works well, especially with large flocks in early season ...I use multiple decoys. I place one or two decoys just inside the tree or brush line, where their outline can be seen, and the rest on the edge of the open area to make it look like the birds are leaving the field (faced towards the brush) I like to put the strutting tom in the trees or brush and hens leading into the trees or brush. When the gobbler enters the field and sees the decoys, he usually comes on a dead run.
I only use this when I'm able to access the area with my cart, since trying to carry multiple full bodied decoys is almost impossible I do use a full bodied goose decoy bag, but its heavy and cumbersome to carry in and out of the field. Full bodied decoys work very well for this scenario, but I can guarantee any decoy will work the same.
Just something I tried and find that works on tough birds.