I've used 100% sheepskin and/or chenile mitts to wash my cars as well as those I detail.
A "key" to preventing marks/blemishes is to rinse the car very well prior to washing.
Also, its important to make sure the mitt is completely "debris free" and clean.
Always, start top to bottom. Never wash lower portions first. Use a separate mitt for wheels. And use plenty of soap.
The towels are used for drying and polish removal in my case.