You let the engines vacuum pull the Seafoam into the intake manifold to clean the engines upper end.. That's the way it's supposed to be done.
Why are you telling the kid not to do something or to take mechanic classes when you yourself don't have the knowledge on the proper techniques??
Now I'm not perfect or a genius but if I can't offer someone a correct way to do something then I don't tell them to give up or take a class... I let more knowledgable people speak up and offer assistance..
The "crud" in the engine (carbon and fuel residues) get loosened up and/or burnt and then expelled through the exhaust.. It cleans the intake, piston tops, heads, etc.. BUT it is recommended that you change the sparkplugs after doing it via this method..