Optimum No Rinse is (in my opinion) the greatest detailing product ever created. Having said that I don't think it's a good idea to fill up a bucket, add some ONR and whale away at the car as quickly as possible.
I've developed my own system for using it on even a very dirty car with no marring or scratches added during the wash and dry process. I've recently corrected my cars paint over roughly a 20 hour period, so I know every blemish and scratch that exists on it. I have been going over the car with a defect spotting light after washing and I think I have the perfect method. It just so happens that The Rag Company uploaded a video to YouTube recently and it is basically the exact same method that I (and probably many others) use.
1. Prepare a 20L (5.2 Gallon) bucket half full of water with 30ml (1oz) of ONR. Add a microfiber wash mitt to soak in the mixture while the rest of the setup is being completed.
2. Fill an 8L (2.1 Gallon) pressure sprayer with water and add 30ml (1oz) of ONR. Pump up to the required setting and set aside.
3. Spray shampoo and/or wheel cleaner and or/all purpose cleaner on to wheels and tyres as required. Leave to dwell for a few minutes and then agitate all areas of the wheel with brushes as necessary. Rinse wheels completely with ONR pressure sprayer.
4. Spray car completely with ONR mixture from pressure sprayer, focusing special attention on any areas that are particularly dirty. I spray until the bottle is completely empty for this one, regardless of how long it takes.
5. Wash car as normal with ONR using slow, straight lines, making sure to rinse the microfiber mitt off in the bucket regularly. If everything above has been done previously, this should result and a fairly clean bucket afterwards.
6. Dry the car with a very plush, high GSM (1000gsm) microfiber towel and use Opti-Seal or Car Wax as a drying aid. I alternate between these two for each wash.
All up this procedure takes me less then an hour to complete, and I can do it in my garage at any time of the day/week. What I really love about it is it's every bit as effective as using a pressure washer, snow foam, hose, 2 buckets, grit guards etc. etc. I was adamant in not giving anything up when using this method as I didn't want to sacrafice anything in terms of the end result. There is no way anyone could ever tell a difference when doing it this way as compared to a 'traditional wash'. There are so many pros to doing it this way (huge water saving, doing it in the comfort of my closed garage, not dragging around a hose or pressure washer for example) I am NEVER going back to the traditional method of washing if I can help it.
I see lots of people who are skeptical about ONR, or who say they have used it and have scratched their paint. What I would (and do) say to those people is 'you are doing it wrong'. It is just as easy to scratch your paint using a traditional wash as it is using ONR, it's just the psychological part that I think people can't wrap their head around. It is quite scary using it for the first time as I'll admit, it sure freaked me out. The end result speaks for itself and after each and every wash I'm blown away by the seemingly witchcraft that comes out of the bottle. It shouldn't be that easy, safe and effective - but it is.