I've got to agree with Joe about the file. I use a paper wheel & strop at home. But, in the field, I use a file, if needed, a diamond paddle & small strop. Broadheads are easily sharpened with a file. The only trick is to always keep the same angle while filing. File the same angle with medium pressure on one side till it raises a burr or wire edge the complete length of the opposite side of the head. Flip it over & do the same to the other side. Make sure you have a burr from tip to the back. Then just stay at the same angle & swipe each side with very light pressure. The burr will soon be gone & you have an edge sharp enough to shave your arm. To refine it, strop at the same angle as you filed. If you use a stopping compound, like Yellowstone or Flexgold, ( from a wood carvers shop) it will really polish it in very little time. The hair on your arm won't stand a chance.
Ray had a good solution too about going to a home improvement store for polishing compound.
I use thin pig skin on my strops. It's porous so it holds a good amount of compound. If the leather is too thick or soft, it will roll up over the edge & dull it.
Always maintain the same angle on every file & strop stroke & it's a very easy job to sharpen a broadhead or knife.