My preferred method of using those types of cleaners are to use the liquid version, hook them up to a vacuum port and slowly meter the contents into the motor. Let about half of it in, keeping the revs up a bit to keep the motor running. At about half a can let the revs fall and it'll stall. Let the stuff that's trapped in the engine soak for a few hours and then re-start the motor and run the remainder of the cleaner through it. Change your oil after you're done to get the solvents from the cleaner out of your crankcase. Pulling and cleaning the plugs after isn't a bad idea either, though an old-fashioned Italian tuneup would probably be sufficient to clear them of any junk from this procedure.
Good luck,
Scott
