When I clean romaine lettuce I wash and spin them dry then just wrap all of them in some paper towel then put it in a plastic grocery bag... I don't think it's necessary to put a sheet of paper towel in between each leaf of lettuce... I clean celery ahead of time in the same manner, wash, dry, wrap in paper towel, put in a plastic bag....I put a paper towel in almost all of my veggie bags
... It's the dampness/humidity that makes them go bad... As for fruits, I just cut as I eat them, to me it's no biggie with fruits...