Success!!! I soaked 6 pillowcases for 2 days. The 4 that were lightly stained came out fine. The 2 that were heavily stained still have some markings. I've hung them in the sunshine and I'll let you know later if that does the trick. Otherwise I'll bet 2 more days of oxi will take care of it. Now I am soaking some of the aprons.
For the record, I'm using the Dollar Tree Oxi - LA's Original I think it's called - or maybe Totally Awesome. I'm using one scoop into a bucket full of hot water, I'd guess 2 gallons. I agitate it whenever I go by, maybe once or twice a day. Today I dumped the whole bucket of dirty oxy water right into the washer along with detergent and a regular load's worth of water.
Thanks for the suggestions ladies!!