Hydrophobic Coating

[Funkstar De Luxe]

Has anyone tried or head of a spray on hydrophobic coating for paintwork? I've used a ceramic coating which lased a long time, but wasn't super Hydrophobic, then I tried Dodo Juice wax, which was very hydrophobic but only lasted a few weeks. I also tried Meguires Detailer Spray, which again didn't last long.

Is there anything I'm missing? My car sits out a lot, and I'm looking for something that will remain hydrophobic for some time.

Tony