Also, I have heard to put a large piece of pvc in the tank that the entire body length can fit into. Be sure it has no sharp edges. Then take out all of the other hiding places out of the tank in the weeks/days leading up to when you want to capture him so that he gets comfortable in the pvc pipe. Buy two ends that will slip onto the ends of the pvc. Then, when he's in the pipe, reach both caps in and put them on both ends at the same time and pull the whole pipe out with the eel in it.
The pillow case should also work but you are going to have to entice him into it, which might be pretty hard to do.