What is the proper / best way to de-carbonize the 4 Mix engine? I just set the valves and changed the spark plug for the first time, was surprised how much carbon was on it. I read that Stihl has a special fluid for the de-carbonizing, but does it go in through the spark plug hole or through the exhaust port, should the valves be closed or open during the cleaning ... if the muffler has to be removed, do I have to use anti seize when reassembling ... Thanks!!