Spreaders loaded with either the BPI 'X' wad or the Polywad inserts work, and work very well. I use both to good effect turning the modified choked left barrels of both 12 and 20 gauge field guns into usable barrels for skeet doubles.

I have not found a reason to employ them in the field, and I likely would refrain.

I'm convinced there is really no safe place in front of the muzzle plane of a shotgun. Pellets can and do fly all over hell.

Even behind one is no guarantee of safety. Pal of mine had to have a pellet dug out of his nose, the result of a bounce off an overhead going away target.

I've never been fond of shooting directly over a dog, I'd not want anyone shooting directly over me...

"The price of good shotgunnery is constant practice" - Fred Kimble