the proper way is to pull the jug to clean it out. you don't want that crap in the engine and there isn't a good way to stop it from getting it in there with the cylinder still on the saw.
I will have to agree with bb^ on this. I just bought a used cylinder off ebay and it was horribly gunked up. It took a little elbow grease and I just don't see a way to keep all that stuff out of the cylinder with it on the saw.