I have been using a 1/2" grinder set up for years as my buffer. Strip off all the guards and the platen from the grinder, and remove the grinding wheels. Install 6-8" buffing wheels. I use sewn muslin cloth wheels. Use a different cloth wheel for the different buffing compounds used. Get yourself buffing compounds. I use several, but there are two that will get the job done. Black course buffing compound, and the green chrome rouge.
Before you even begin to start buffing knives there are safety concerns. Bufffing is dirty, and if you don't have proper dust collection and filtration equipment, then do the buffing outside.
2) Where a good leather apron, goggles and good shoes.
3) Practice buffing on a length of pipe first. Learn how the wheel reacts to the pipe. Buffing wheels like to grab things and pull them out of your hand, and before you know it, the buffer can throw it back at you with deadly results. Thats why you should buff something round like a pipe first. You may also want to practice with a piece of flat bar too.
4) Before buffing any knife surface, be sure to grind/hand sand down to at least 600 grit, but better yet to a 9-15 micron finish. Then go to the black compound. Coat the wheel thoroughly, as it spins. Now apply the blade to the wheel and pay attention to what you are doing, and where the blade is on the wheel. Faster than you can react it will grab the blade if you are not carefull, and watch out where the tip of the knife is. Concentrate on what you are doing. If you are in a bad mood, then DON'T BUFF!!
As you buff you will need to constantly add more compound, as it blows off the wheels quickly. Check your work, if the scrathes are not coming out do not use excess force. Shut the machine off and go back to the sandpaper, then return to the buffer.
Once the scratches are gone, replace the wheel and go on to the green chrome rouge step, and repeat until you have a mirror polish. Be patient, buffing can be a tricky step, and for it to work, all sanding must be done properly before hand. DON'T HURRY, AND DON'T BE IN A RUSH.
