caught in the rain!! recommended billboard cleaner

[culp71]

Despite my best efforts, during my last drive out it was blue skies and I was about 1 minute from home when it decided to down pour... first time the car has seen rain.

I pulled into my garage and quickly dried entire car and proceeded to clean entire car and wax exterior using wizard brand supplies.

my question is what about the billboards?
I did not wax them of course, simply just dried them off with a bath towel.
(they are the flat black 340 style.)
I did apply one coat of SLIDE-OVER UV Protectant from phoenix graphics
while I did not see any water spots I want to make sure there are no minerals sitting on the vinyl that may cause damage or discoloration.

what is the best cleaner to use on the vinyl billboard graphics that wont cause damage or make them appear shinny, greasy or discolor them?

thanks

[Skdmark]

I would wash with clean water and Dawn dish soap. Use a microfiber cloth to dry.
I don't have billboards, but have a 71 Challenger with vinyl side stripes. Never had an issue.

[tparker]

Out of curiosity, why the concern over the rain? Water spots or something else?

[culp71]

yes, water spots, I got some on my new truck and I had to buff like hell to get them off, I don't want to have to buff the cuda especially the billboard!   
I don't want the hard water spots to appear on the black billboards, so I want to get it cleaned off properly ASAP.

no real other concern with the rain, is there something that I should be?

[tparker]

I don't know. That's why I was asking. LOL. When it rains here, we get lots of dust, which is worse than the water spots. It's horrible. It's a sandy dust

[anlauto]

I use to use Windex in the hot sun, not that I'm recommending that, but I never had issues...

[Racer57]

Rain water is soft water.