I use a belt grinder. start with coarser belts like 120 grit (depends on how much steel you need to remove initially) and work up to finer grits. I usually stop at 400 but occasionally go up to 600. You can then strop it with a stropping belt or strop it off the grinder with a leather belt or stropping board. I prefer convex edges and convex my EDC folders as well as my user fixed blades. the angle of the convex can be changed to make it thinner/sharper or more meaty for hard use. I think it is a stronger edge and it is capable of being very sharp (Its great for chopping). There are several others here current and past that are big fans of convexing as well. Good luck!

My typical process would go something like follows:
120 grit - to get the basic convex shape- remove steel
320 grit - start to grind out roughness
400 grit - rough polish - then leather strop with stropping compound -- OR skip stropping here and go on to...
600 grit - finer polishing - and then do the stropping. I rarely go above 600 grit.

Obviously, you wouldn't start at 120 to re-sharpen an already convex blade- just go right to 400 or whatever. <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />