Leveling my hunter's weapons was a pain at first. Normally I'd run through RFC/SFK or whatever attacking everything melee, or send my pet after a mob, let it tank while I sit there auto-attacking. Both of which required too much attention and effort for my lazy self. I consider this an exploit as I'm sure blizz with "fix" it if they realized it can be done, wingclip causes damage so it's not working as intended, and other ways, imo, require much more effort for the cost on not missing a wingclip due to weapon skill.
Go into RFC or whatever, would probably work on any mob, i just use RFC so no idiot comes up and kills the mob attacking me. Get a single mob attacking you from behind. Make sure aspect of the viper is up for mana-regen. turn slightly to the right, making sure the mob is a bit to the right of you spamming your wingclip button until it lands. You'll notice a "You are facing the wrong way" error message, but you will still get skillups, you will not kill the mob (or even hit it with any damage, only the debuff), and you can just spam-press or click while you're watching tv (like i did). I guess its also possible to use an auto-clicker to continue spamming wingclip while you walk away. Oh yea, in case you're wondering how i figured this out, it wasn't taken from anywhere. Before I figured this out i would pull a bunch of mobs in RFC and let them crowd around me so I could just auto-switch and wingclip over and over, one just happened to be to the right of me and I noticed I wasn't damaging that one. Tried it a bunch more times and it always works. You can even drop an frost trap and freeze them, still hitting them with the debuff without removing the trap. (which i also think is pretty cool)