This is what I do also. Sometimes, if the marks on the tank aren't bad, I just use a wet paper towel to wipe the marks off, and a dry paper towel to dry off the glass. As Lucy said, soft cloths are much better than paper towels if you have an acrylic tank.I spray windex on a paper towel, then wipe the glass. Never spray it directly on the glass, droplets could get into the tank.
If you have an acrylic tank, use a soft cloth.