If I have an engine that's being taken out of service I will make sure the insides have a good light coat of oil to keep the inside of the engine from rusting and going bad. But for "after run" oil I don't worry about it. I run the fuel out of the engine, clean up, and load up the plane. I've tried after run oil in the past and IMHO it's just an added step (and expense) that isn't needed. I also feel that when I used after run oil I seemed to go through glow plugs quicker. Without after run oil I have glow plugs on their 4ths summer of flying!!!!

Ken