Here's a pic of the setup I use for sanding/drawfiling. I took the idea directly from Wayne Goddard's book $50 Knife Shop. It consists of a one-inch block of wood made from a split 1x4. There's also a piece of steel taped to the underside of the wood to keep the clamp from crunching it.
**Disclaimer - I'm VERY new to this.**
On the project shown here (my first), I started by drawfiling along the the length of the blade, mostly pushing away from myself. Then I graduated to a wood block with sandpaper, and finally followed with the leather beanbag with various grades of sandpaper. This resulted in a convex profile with a surprisingly (to me anyway) straight edge. Hope this helps.