Maril555,
I have RPG skylines that I had RPG paint for me. I do not know if they used any type of undercoating when they paint them but they did use the exact paint that I specified for them that I used on my ceiling - same brand, type and color. By looking at them, I would guess that they use a paint spray gun to do this as the paint is very thinly applied. YOu could probably just call them and find out the specifics of what they do. I would also agree that it would be very difficult to cover them with an acoustic fabric. Covering something with acoustic fabric usually works best if you are covering a smooth, flat surface which as you know is not what an RPG Skyling is. I suspect you would need to do lots of cutting of the fabric to make this work effectively. Painting is the way to go.
