If you haven't murdered someone yet and you don't want to join the dark brotherhood then just read this.

If you are doing a mission for the Arch-Mage Traven and the Count of Skingrad to kill the vampire hunters: start with the one outside and if a guard catches you assualting him run away with the gurad and vampire hunter chasing you.
Just go into the wilderness and wait for a bear or anything to attack them once the bear is dead or alive kill the bear.
If the bear killed the guard and vampire hunter then repeat this again and again, and you can also use fighters guild members and mages guild members to help kill off the guards and vampire hunter(s).