Do not turn return pump off, but skimmer off for a bit would probably help effectiveness.
However! You may want to make sure you are "fixing" the right problem first.
If you have a low nutrient system, those products might help quite a bit. (so would feeding more)
But if you actually have something like high phosphates/nitrates, they will make things worse.
And in general:
There are no miracles in bottles.
Beware of over-complicating things.