There are numerous waterless wash/polishes on the market and I had always been somewhat wary of them until I watched (in horror) someone cleaning their quite filthy caravan windows using the magical stuff.
The owner of the van hadn't cleaned it during his 6 week European tour and their was crusted sea gull poo, dust, squashed flies etc. etc. all over the van including the windows............... well squib, squib, squib, a quick agitating rub with one micro fibre cloth and then a final buff up with another micro fibre and the windows looked like new without even the faintest signs of any scratches.
I have been using this stuff now for about 10 years on everything from the windows of my house to the Seitz windows fitted to 'Millie' and it never ceases to amaze me how fast it is to use and what a truly brilliant finish it gives........... Mind you having said that, I do normally wash off the worst crud before starting to use the spray polish.
My classic car, shines like new and I even use it on the plastic back window of the soft top and finally one of the advantages of the polish is that you can even use it on the black/grey plastic trim that normally looks horrid when normal polishes have been used.