Interesting, this is the first time I hear that touching fomites is the primary vector of spreading. The CDC page says the opposite: https://www.cdc.gov/coronavirus/2019-ncov/prepare/transmissi... But I do appreciate that we still have a lot to learn about the virus, so disinfecting your hands frequently and being careful about what you touch is sound advice.

The other benefit of masks (and probably the main one of DIY masks) would be that it decreases the chance of the wearer infecting others.