There was a paper that went by my Twitter feed yesterday about how dish towels tended to do better on the particulates the researchers were testing on than a t-shirt (or piece of silk, or double layer cotton shirt, or...). I agree about them being better than nothing and it'll be fairly dependent on aerosol size but you should probably prefer thicker clothes.
Dish towels and vacuum bags do a better job of filtering, but make breathing quite difficult. A simple cotton t-shirt material is fine. And there's no sign that double layers help; and they make it harder to breath as well.