Yeah, ideally after run should be used all the time. The point to it is to displace water/moisture on the parts so the engine/bearings etc cant rust. A few drops wont do much, you want a decent supply of oil in it. You dont have to douse or flood the engine with it, except for very long term storage. You want enough to get in and coat the bearings, crank, etc. Put several drops in the head, but if you dont want to take the plug out each time, put it in the carb and turn it over in order to distribute the oil well. If oil is placed only on the head it cant get to the lower engine parts as easily and that is where it is most important.

After you fly, run the engine and carb dry of all fuel then put in the oil. The less fuel you have to contaminate the oil, the better.

Its like the idea of WD-40. Not that you should use that, but the WD stands for water displacemant.