Old School is correct. Years ago, before the introduction of microfiber, we used baby diapers as they were much softer than terry cloth. I will stick with the microfibers for wiping the paint.
even back then, there would good diapers and bad diapers. All to common they had ribbons of polyester and could scratch. With the advent of MF there is likely not many still using diapers or suggesting their use.
Diapers and t-shirts are cotton and have a flat sheen
Microfiber is a blend of nylon and polyamide fibers and because they're miniaturized they become more gentle to scratch sensitive surfaces and coatings as compared to the larger fiber cotton fiber products. Nylon and Polyamide, which is a type of polyester, have traditionally been considered to scratchy to be gentle to sensitive automotive paints, but when they are miniaturized, the microscopic size of the fibers change the physical dynamic of how the aggressive or in this example how non-aggressive they are to automotive paints.
For final wiping, stick with microfiber.
Met a guy while teaching a class for the National Corvette Restoration Society that had his car repainted and Afterwards only used soft Flannel to wipe-off products from the paint on the advice of his painter. His car was silver metallic and he though it looked pretty good. In front of at least 30 of his peers I pulled out the Swirl Finder Light and revealed all the scratches in his paint.
He quit using flannel that day.
Flannel, like diapers and t-shirts has a flat sheen. Flannel has a fuzzy flat sheen, but it's still not as gentle to automotive paints as quality microfiber.
Mike is the man.
Great explanation on diaper cloths. I too have used diapers ,20 years ago, but now things are different. The new microfibers are much better for the paint. Plusher and softer.
If you have a few diapers around I might use them for the wheels, door jams, or engine bay. my .02 cents worth