Kettlebells work better than dumbbells for flyes. Because of the position of the resistance, the pecs are under load for a greater proportion of the range of motion.
With dumbbells, the muscle tension on the pecs is greatly reduced at about 60% of the range of motion. This can make the reps less effective, especially when you're using a method where you must maintain constant tension to create an occlusion effect.
As a young man in the iron game, Mike was surrounded by people who drank the pro-bodybuilder Kool-Aid. He never squatted ('cause it hurts your knees) and never deadlifted. Now he knows better.