Brad,
It was an Onsrud 65-025 1/4" Solid Carbide One Flute Upcut Super O Flute. It is a general purpose Super O. I used the same bit today to cut some HDU and Ultraboard. It is a good bit to have.
Joe,
For these letters my customer is just going to paint them with some latex acrylic and put several coats on them. The cut edges are smoother than the surface believe it or not. He is going to sand the surface a little. He just did a tree in styrofoam for a church and he coated it with some trucrete and painted in with the latex acrylic.
My customer is a very creative guy. He and his dad created several of the signs at Dollywood. I'm in awe of some of the signs that he has in his shop that he created then replaced for a new design, new change, etc... Some of the effects that he uses on his signs in amazing.
Andy B.