Actually the bottom ( I assume you mean the skirt part ) I just used a work out mat from Wal-mart, cut the sections then glued a strap to the back to the pieces so it had plenty of flexibility for when I sat down. Most of the other textures you see are just thin layers of bondo painted on with a 1" brush so it left a streaked texture. then before the bondo fully set I took a good razor blade and trimmed off the unwanted edges.
It was made from paper that I backed with plastic (most people use fiberglass) with the help of a program called pepakura. I still do have the files i used to make this so if you need just ask. Also check out the rest of my gallery and see how the new version is starting to turn out.