Whats the best way to clean microfiber towels so that they will continue to be gentle on a car's finish? I've heard things such as not using detergent, no fabric softeners, etc..
You want to use a detergent that is free of fabric softeners and unecessary chemicals. I use All Free and Clear myself. Another tip is to put 1 tbsp per towel of white distilled vinegar in the rince cycle, this will break down any remaining detergent so that it doesn't build up in the towels. Dry the towels in the dryer with low heat.