Use a car wash detergent that contains wetting agents. Those are additives that cut surface tension so the water doesn't bead. When you rinse, flood the surface with a solid stream and let the water sheet off. Then use a blower to remove as much residual water as possible, follow up with a soft cloth.
If you don't mind spending some cash, look for a filtration system that creates deionized water. You can buy the filters and rig up a system for your rinse water that will be just like what they use in car washes for the "Spot Free Rinse". It won't be terribly inexpensive, however.
Jerry