Hello UNC Nick,
I actually use a 16" x 16" mf towel to wash my car with but as ejant has mentioned it could scratch the car if it gets overloaded with dirt. To prevent this, what I usually do is wash couple panels of the car with the mf towel then I thoroughly rinse off the mf towel. However, do not "double dip" into your car wash solution if you have not rinsed off your mf towel first. Because if you dip your mf towel in without rinsing it off first, it will release some or all of the dirt into your shampoo wash bucket. So best thing to do would be to rinse off the mf towel in another bucket of water. I don't know if you know the "2 bucket" method. One bucket is filled with your shampoo wash and the other is filled up with water. As you go, you should always rinse off your wash mitt or mf towel in the bucket filled up with water before dipping your wash mitt or mf towel in your shampoo wash solution. This prevents your shampoo wash solution to get contaminated with alot of dirt. It takes a little more time but it is the Autopian way...:xyxthumbs
I hope that helps.
With Aloha,
~Ranney