I use an expensive commodity, i.e. water, and use Mer to clean off any marks. I've never used soaps in all the many years I've owned cars and have been happy with the results. I always clean thoroughly though, eg round the door hinges etc.
You can spend a lot of money on all sorts of cleaning products, but all you end up with in any case is a clean car.
Valet Pro Citrus Prewash & rinsed, then snowfoamed & rinsed, then washed using Zymol Auto Shampoo using 2 buckets and Car Pro Sheepskin Mitt & rinsed, Dried using large drying wooly towel, IronX, Rinsed, Clayed, washed and rinsed, dried again, Machine polished using Megs range, sealed using carpro CQuatz, Glass polish then sealed, wheels sealed with Planet polish wheel seal, trim & tyres dressed.
Wow a lot of time and hardwork! I use greased lightening on my perl white ds4 half hour later sparkling with that smooth polished feel and the rain water just beads of the car! Use it on alloys and glass looks mint highly recommended,best of all no water in sight!