To be honest, we do not recommend Waterless washes.
Few reasons;
Firstly, when you have to use approx 5-20 cloths to ideally be as mar-free as possible to the paint you will end up costing yourself a fortune in washing and of course replacement of cloths (providing you do not have quality cloths, which of course still cost more but can offer 200+ washes).
Secondly, when you drag any cloth clean or not clean across the surface the contaminants, dirt and debris on the surface drags ALONG the surface and even with lubrication has a high chance of marring the paint. This is another reason why they invented the Snow Foam Lance, to pre-soak the paint which helps aid the removal of dirt before any friction is caused by the wash mitt during the wash process.
Lastly from experience side we have tested this theory thoroughly in early days of car washing and recently again with panels to compare how much marring is caused - unfortunately, still quite significant.
Its really up to the user and how pedantic you are about your car at the end of the day to be blunt.
If you're a wash and dry the car with a sponge and chamois and whatever car wash, so be it - this would be as impacting on the paint and causes "spider webbing" (marring) of the paintwork within 2-3 washes.
If you use 2 Buckets (1 for wash, 1 for rinse), a soft microfibre or lambswool mitt in combination with a microfibre drying towel (waffle/normal) and a pH Neutral wash, you'll drop your chances tenfold from marring the paint.
On a quick note, there is the "
rinseless" wash which you can use the two bucket method which offers much more lubrication from Duragloss here.
Underside of the car, 1Z Einszett W99 works incredibly well. Recently did this and surprised how much came out from the arches and under-body! Definitely use a high pressure washer in combination as well if you can