This is going to sound stupid and keep in mind I'm far from a competent crow hunter. However, I've purchased 5 of the dove decoys from Walmart for $2.50 each. Then I bought a can of flat black spray paint and painted each of the dove decoys black. Also bought an owl decoy in the lawn and garden section of walmart for $19.00.
I clip four of the dove decoys on branches in a low hanging tree, put the owl decoy on a fence post about 15 feet away, and put one of the black dove decoys laying on its side on the ground at the owl's feet.
Then I fire up the foxpro and sit back and wait. I've killed several crows this way, but no where as many as I'd like. The crows come in decent, but tend to realize something is up pretty quick. However, it'll work.