Time to start painting. First I had to determine what kind of paint was already on the green panels. I did this by dipping a rag in denatured alcohol and rubbing it on a painted part near the bottom where it wouldn't be noticed. If the rag took off the green paint then it is acrylic. If not, it is oil paint. Here is the original color.
Well, it turned out to be oil, which is what I suspected since it is pretty old.
I then rubbed the entire screen with a towel soaked in alcohol to clean it. It already looked clean but...
Next I painted a thinned-down coat of kilz original on it to cut the green down a bit - windows wide open! I will probably paint a second coat of white tomorrow when (if) this is dry. Then I will be ready to transfer the drawing to the white surface.
These preparation stages are tedious and oh so boring but necessary.
Stay tuned. Hopefully it won't rain this week so I can keep painting.