Clean Towels . . . works great . . . found another suggestion to add 2 tsps dawn dishwashing liquid to vinegar load. Doesn't seem necessary, but good to know. Be aware - dryer sheets build up residue on towels over time.
Towels would seem to be such a utilitarian object that they could never need any sort of optimization. As your towels age however, their absorbency decreases. Boost them back to their glory days with this simple hack.