I took the rear off and ran my fingers on the inside. I didn't need tissue or a cotton ball as the trail of blood lead me to the wire.
Next time I'm using what has been suggested. Don't use fingers.
Anyway, the rear was going flat from a previous puncture and had two additional pieces of wire that didn't yet penetrate the tube.
The front had a bent piece of wire that made two holes very close together. I ran out of tubes last week so I am patching all of these.
Thanks for these great tips! I am sure that the piece in the rear would have yet caused another puncture. I was going to buy a liner for the rear but I think a close inspection post ride should do the trick.
There is no way to avoid these tiny pieces on the road so I have no idea how many are still laying there or how long they will remain on the road.