crazy train. The best crow decoys are dead crows themselves! You are on the total right track with the owl setup as I've been shooting them since the mid 70's and have killed thousands.
Have refined my setup to a single plastic owl (my stuffed one got the stuffing beat out of it years ago) perched on a 7 foot wood fence pole. Screwed on an old trebble hook to the owl where it's talons are. Hook a dead crow to this hook and it looks to the crows as the owl has a crow in it's talons and is beginning to dine! Break the crows wings and they will dangle in the wind for an even better effect!
Put this setup in the open where crows fly or frequent such as a flyway or feed lot and with a good bit of hand calling or an e-caller... you will have a shoot. Just make sure that your well hidden with clear shooting lanes above, that is no tall overstory.
Practice hand calling as e-callers are not the be all end all to getting high body counts. Learn the mourning call, use it when crows are hovering over already fallen comrads, crooning, you will suck them in almost into your blind!
Facinating birds to hunt, smart and tough to hit at times. Shoot a more open choke with trap loads and no shot size bigger than 7 1/2.
The first time the "planets line up" and ya kill 40 or 50 crows, believe me you'll almost give up upland and duck shooting!