Firstly - ditch the sponge. Get a lambswool or similar mitt. They draw dirt into the pile, whereas with a sponge the dirt just remains on the surface of the sponge.
The spray gun detailers use is this:
http://www.carcareproducts.com.au/pr...now_foam_lance
I have this exact one, but sourced directly from the UK for less than price offered here.
Important to hose off car at least once before actually putting any mitt up against the paintwork - so think of it as a more effective pre-rinse wash.
When drying, you can minimise effort by partly blow-drying the car with a leaf blower. Make sure the blower doesn't touch the paint. Then you can also use lube (either a quick detailer spray or something like Optimum Car Wax) whilst towel drying. The superfine droplets left behind will dry without a trace in a few secs.
After that, scratches will just naturally occur if the paint is touched during daily use. But since these cars are designed to be driven and enjoyed everyday, that is a small price worth paying even if you enjoy a nicely detailed car.