What type of heads are you using? If it's replaceable blade heads, just buy newblades and don't use 'em till you're in the woods. Use the dull ones for your 3-D target. Heads like Razorbacks, Snuffers, or Montecs can be sharpened with a flat stone and strop or file. Magnus recommends using a file and leaving it at that...burred and what not. Says the edge acts somewhat like a serrated blade. As for two bladed heads, I'd use a file to shape and a fine diamond stick-type to hone and put the edge on. I've heard it said that you should be able to slightly angle the blade(s) on your thumb nail and it should stick, not slide across. Also, slicing paper or shaving arm hairhas been said to be an accurate indicator of sharpness. Reguardless, when sharpening, remember to apply medium pressure initially to achieve thedegree/angle of the blade, and light pressurein the end to hone thatblade. Try to match the "factory"angle on the blades...not too steep, and not to shallow an angleeither.