Sorry it took so long to respond. (It's Christmas -- the busiest retail season.)
I get my sharpening wheels from Kovals Supply http:\\
www.kmg.org/kovalknives.
I use the 8" wheel on my 6" grinder and the 10" wheel on my 8" grinder. You will have to take off the guards. But it lasts a lot longer that way.
First, you will have to either just turn your buffer around or take the bottom off, unbolt the motor from the base, turn around and rebolt to the base. This is safer because the switch is now facing you.
Sharpen off the top of the wheel. Practice with the grinder off for the first couple of strokes to get the right idea!
Place the knife with the edge of the blade facing away from you, and the knife laying perpendicular to the wheel. Start at the end closest to the handle and pull the blade toward the tip, horizontally across the top of the wheel somewhat like this: ==[]=> (Knife ==>) (wheel []). Try to maintain a 15 degree angle at the edge (just like using a stone). As you get to the tip of the knife you will have to pull the handle up a bit to maintain that angle. Work with smooth strokes, dipping the blade in water after each pass.
It takes a steady hand, but not alot of pressure. The diamond gritted wheel will take a surprising amount of metal off. It should only take a stroke or two to pull a burr on one side. Make sure you can feel the burr before you switch to the other side. Create a burr on that side (again only a stroke or two).
Next go to the slotted cardboard wheel. On this wheel, do a pass, dip, then switch sides of the knife and do another pass. You will be able to see the burr polish off. Different steels pull the burr off in different ways. With some steels the burr curls off, others it flakes off.
It just takes practice and care not to over heat the knife.
Good luck and email me or post questions and I will try to help you.
Pam