I've used the Azek "boards". It's solid pvc. They were smooth on one side and textured wood grain on the other. They glue up with pvc cement and WILL NOT come apart. Carves great. Azek says to use acrylic latex paint (must be the plastic to plastic bond). I used water based Rustoleum on the first one and it didn't last thru the winter. If using the textured side it's best to paint the board first and then cut, leaving either white or brown pockets. It's awful hard to clean up with all the nooks and crannies. It has it's place.
For big jobs the professional sign guys around here are using Corafoam by Duna. Comes in sheets in different densities and thicknesses up to 4 inches, I think. Won't bend, break, or warp. They're using 100% acrylic paint, no finish coat, and guaranteeing them for 10 years. Love the way that stuff cuts.
RoutervilleUSA on Etsy
I took the tests and retirement is the best job I'm suited for.
Now I know why old guys wear suspenders.