Once you unlock the elevator shortcut from the upper undead burg (just before the gargoyles), you can use the crow's nest to fly back to the Undead Asylum. Each of the torch-wielding ghouls drops 100 souls and with the dragon sword you can one shot them. There are not one, but two bonfires nearby and you can kill 6-8 ghouls right by the fire and respawn them every 40 seconds or so.
Just do NOT stand in the middle of the room or you'll fall through the floor and have to fight the Stray Demon, who is very beefy. --- Someday, someone will best me. But it won't be today, and it won't be you.