[moosecat]

I know about mm and drylock. But, I'm carving a castle wall out of pink foam panels. It's 50' × 10'. Is there anything I can spray on for weather protection? A brush will take forever.

 

[Deadna]

I've always used outdoor house paint for my foam tombstones and never needed to seal anything...except for the time I painted all the foam boards for my windows and we had a storm that night that completely washed all the paint off
If they are good and dry they should be fine. After you have a coat of paint on the foam you can spray on anything you like if you want...the foam won't get eaten away once painted first.

 

[stuffyteddybare]

to cover large areas I use a garden sprayer...the tip should be almost closed so you get a shower effect versus a loose tip which would give you a stream..spray your light color first and then use your dark cover.. you spray it on so it doesn't cover all areas..and you use both paint colors like that... it gives it a stone like appearance..