If it's the cast iron piston then it needs a very special running in procedure. It seems strange that the hobby shop guy mentioned slobbery rich and then ABC though. I have to wonder just how many of these engines have been ruined from not knowing how to run them in properly

The following link gives the best explanation I've seen as to why they need to be run in properly and then how to do it. Although it's written for small diesel engines the principle is exactly the same for a glow (same metallurgy). Oil type and content should be the same for a glow but even after it's run in I wouldn't use less than about 22% oil and half of that castor. Then it'll last forever

http://www3.telus.net/dieselcombat/breakin.htm