I wouldn't do it that way.
Note that on many Grady cushions, the foam may be covered in a plastic wrap. The foam itself is not like the newer dry foams and will get wet and stay wet if exposed to water.It will grom mildew. Removing the foam may mess up that wrapping.
If the cushions are dirty on the outside, try mild soap and water first. If there are stubborn stains, after the vinyl dries, use acetone. Grady recommends acetone for cleaning. Do not use abrasives or Magic Erasers. They will remove the outer protective layer.
If things clean up, dry and treat with 303 Aerospace Protectant.
If the cushions have mildew or mold, it mat be coming from the inside out. That is a more difficult problem to tackle.
If the stains are pink, you have a problem that is almost impossible to fix. It was a manufacturing defect in the vinyl itself.