I typically disconnect the fuel line, and start the engine till it won't start any more to ensure all excess fuel is burned up inside the engine. Then, I get all the fuel out of the fuel lines and the tank, and put a few drops of after run oil in the carb and the glow plug hole. All after run oil is, is Dextron III automatic transmission fluid, just the stuff at the hobby shop is $2 for a two ounce bottle, and the stuff at the auto parts store is $2 a quart. You shouldn't have to worry about the remaining fuel, but if you want it all out, try getting a fuel bulb or turning the fuel tank opening upside down over the fuel bottle. But no matter what, there will still be a trace amount of fuel in the tank.