There is a Nano product that is sprayed on cars after delivery
to protect finish. A similar one is used on glass buildings to obviate need for window-washing and another on all surfaces in hospitals so bacteria will not stick avoiding in house acquired infections. The Nano material fills all the surface's interstices, even those in glass so nothing adheres. I got the idea it was like a permanent 'Rain-X' coating. It's very big in Europe
I investigated it a while back and bought one liter which is sufficient according to the manufacturer for 55 cars! You need a cheap
bug spray to apply reducing the spray to the most minimal output possible.
I was planing to spray my slate roof after steam or spray cleaning
, but so far have not found someone who will work on a wet slate roof in Miami
- too slippery. The idea was to prevent mildew accumulation which again according to the manufacture should work.
The company that sold it to me isn't interested in retail, but rather in doing the whole job usually entire hospital interiors for example. Sadly, my roof was too small to interest them.