I put the oxy-clean directly onto the leather and rubbed it in just before I put it in the washer. I don't know if it helped but it didn't seem to hurt it!
I usually buy net lingerie and/or sweater bags at JoAnn Fabrics and use them for machine washing delicate items, but I am sure that a pillowcase would work just fine.
My Tory Burch wallet is a bright orange color so I washed it by itself. If it was a darker color I might have put a couple of other dark leather items into bags and washed them all at the same time.
I have used woolite to wash leather goods before and it worked fine. I do like the leather therapy laundry solution but it makes my washing machine smell like leather conditioner and I don't want my clothes to smell like that! I always run an empty rinse load afterwards just to get the odor out of my washer. Good luck!