The aerosol version of Seafoam doesn’t dispense at a fast enough rate to raise the compression ratio of the cylinders to blow the carbon off.
I’ve used Seafoam products for over thirty years. And if I thought the aerosol version would work, I would have suggested it.
Tester
The problem with the penetrating oil suggestion so many have mentioned is that the spark plugs have a very effective seal between the combustion chamber and the outside world. The spark plug threads are, unfortunately, on the other side of that seal. As OK says, break the plugs loose a little, THEN apply the penetrating oil. Or, as Tester says, apply the penetrant from the inside, using the running engine to draw it in.
Applying penetrating oil to the outside of a seated spark plug won’t get the threads even a little bit wet. Ever.