I really never apply any oil when rebuilding my RC car engines. Now with the bigger 2 stroke engine i always to but with these i don't. But if you want to you can put a drop or two on the bearing inside of the crankcase and you can also put a drop or two on your fingers (make sure your fingers are clean) and just run your fingers over the crank just to make a thin film coating on the crank shaft. Then when rebuilding larger 2 strokes i always use plenty of 2 stroke oil (you can use after run oil in the RC car engines) and put some on top of the piston then rub in all around the piston including the sides. Again make sure there is a film of oil on the piston. You can then take you finger and since there should be still some oil from the piston and crank and slip it into the sleeve and make sure that is lubricated. Then rebuild and with the glow plug out then turn the engine over just to disperse the oil over all the engine internals that you might have missed.

Now as i said is usually don't lube the engine when rebuilding these smaller engine and everything i described i use for the larger 2 stroke engines. But everything i said you can do to lube your engine. As I said i never really lubricate any of my engine when i rebuild them and i have torn apart plenty of engine (just to clean them up and see how there doing) and have never had anything bad happen to any of them. But if you want to just do what i said and you should be more then fine.