Here's how we do it:
With the broadhead perpendicular to the rotation of the wheel (6 inch grinder, medium grit wheel) draw it from back to front, applying light/medium pressure on the head. Be careful to keep the 2 blades that are touching the wheel even (don’t “rock” the head up and down) and do not go down off the tip and blunt it. Also be careful not to overheat the head (will remove temper), I keep a bucket of water handy. You don’t want to develop any blue color on the blades-it takes quite a bit of heat to hurt them, though.
You are finished when you have a completely new, even cutting edge along the full length of the head.
These are really sharp enough to use now, they will not shave, but have a “burr” edge. I generally prefer a shaving edge and go on to the next step.
Using a hard black Arkansas (or any other hard oilstone) place the head with 2 blades flat on the stone and move in a circular motion with medium pressure. You will feel the metal coming off at first and after 10-15 circles it will start sliding like ice. This step is finished when it slides slickly.
To achieve the final nasty sharp edge draw the head backwards on a piece of hard, smooth leather 6-8 times per side (2-blades flat on the leather). Some guys put fine jeweler’s polish on the strop, but I just use the leather. Put Vaseline or some other oil on the cutting edges to avoid rusting and you are ready to go. I occasionally strop the head a bit during the season to touch it up. This full process will only take a couple of minutes per head once you have the grinding step practiced up.
I hope this helps!
For extended trips, or hunts where I expect alot of shooting I take a Razor Rake pull through sharpener and a file, but for pre-sharpened heads the above process is the easiest and best we've ever found.
Ryan