if you are doing a cleaning, the best way to do it is to start out by pouring half the can into your fuel tank, and give it a 10 minute or so drive to get the engine to full operating temp. this will also give the seafoam time to work its way through your fuel system and thus injectors
after that, you get a friend (to keep the engine rpms up to prevent stall) and pour the last half slowly into the induction system via brake booster. the bake booster line is always the best one to use, as it uses vacuum directly from the intake manifold. this will give you the most direct route, and an equal distribution through the intake valves
after the can is poured in you let it sit for about 5 minutes, not an hour (that lets the engine cool down too much, you need a hot engine so the seafoam can react to carbon buildup). then, you restart, and do some good revs and watch the smoke ensue your driveway as well as your neighbor's
as far as not having enough buildup, depending on mileage and whenever the last time you did your cleaning was i would say this engine has plenty of buildup every 20k miles. ive gotten plenty of smoke from induction cleaning after that mileage
the other way to use it is maintaining, which i do often. it's when you introduce seafoam into the gas tank only. i do this about every oil change to keep the injectors and exhaust side as clean as i can
the final way to use it is through the crank case. but i would do this the least often as you need to do it just a few hundred miles BEFORE your next oil change because it breaks your oil down so much