There are a few CQuartz coatings.
https://carpro.uk.com/collections/cquartz-coatings/products/cquartzuk30
http://www.cquartz.co.uk/finest
and
http://cquartz.com/product/cquartz-finest/
The top one is the cheapest with the other two being more expensive. I had Finest put on my S4 when it was new and was very happy with it. In terms of maintenance normal shampoo will do the job. I supplemented this with a monthly wash using Carpro Reset shampoo:
https://carpro.uk.com/products/reset500
The coating does mostly just look after itself. If the beading drops off the Reset always brought it back. Periodically I would top up with Carpro Reload:
https://carpro.uk.com/products/reload-inorganic-spray-coating-500ml-2015-edition
However I found it's a pain on black and have now switched to Gyeon Cure instead mixed 1:1 with water.
CQuartz Finest lasted the advertised 2 years but I had my car recoated shortly after this as I had general wear and tear from my work's car park that needed polishing out anyway. For me I find it's worth the money to have a pro detailer applied coating. The cost is comparable to the (hopeless) dealer products with the difference being the coating is properly applied with the paintwork fully prepped first. On both occasions my car has spent 2 days with the detailer, one of the reasons being a ceramic coating really needs overnight in the dry to properly cure. I don't have a usable garage so DIY isn't an option for me.