Stefano da Bagnone - Silent Shortcut
http://www.youtube.com/watch?v=evyO2cllo9s
A quick way to eliminate most of the guards in this mission while remaining unseen is to hire the mercenaries to fight for you. Guards will automatically join in the fight if they can see the battle, so all you have to do is get the battle started in a central location.
The problem is that you cannot lock onto the disguised guards in this mission, which means that you can't order the mercenaries to fight the guards. The funny thing is that you can lock onto the monk that walks alongside Stefano - He's considered an enemy in this mission for whatever reason. Wait for him to reach the central area of the cloister, and then give the order to attack. A quick battle ensues; the mercenaries greatly overpower the disguised guards.
Stefano will wander around to inspect dead bodies as if nothing weird is happening. He will flee to the abbey if he takes some collateral damage from the battle, and he will also flee to the abbey if you order the attack on him directly.
If you are interested, here is the "long" version of the silent mission on Stefano da Bagnone.
http://www.thehiddenblade.com/silent-prayer-stefano-da-bagnone
Stefano: Hmm, look at all my guards dead on the ground, and those hulking mercenaries with huge axes standing right there... oh well, let me just stare in the opposite direction and hope they go away..." *stab*
"When you have to kill a man, it costs nothing to be polite."- Winston Churchhill
"Kill a man, and you are an assassin. Kill millions of men, and you are a conqueror. Kill everyone, and you
This was a really useful and interesting method. I've never been much good at this mission, depsite how small it is, and normally just run or ride away afterwards. Very clever!