Originally Posted by JARblue

I bought a foam gun in the first year of owning the Z. I liked it a lot, but it's not a high quality one. I used special foaming wash and had to use a lot to get a nice, thick layer of foam. I was happy with its performance overall, but I only used it a few times for exactly the reason you mention - sun drys it out. I just gave away the last of the soap to my neighbor, and the foam gun is sitting in the same box it has been for the last three years

I generally wash my car in the sun and have zero issues with water spots