Some of this info has been stated already, but hopefully by placing it all in one post it'll help you.

The first thing you'll want to do is mark the locations on your map if you have the mod to do it. It made running to each spawn point easy.

Start at...
27,51 then head SSE to...
32,62 then SE to...
35,65 then south to...
33,71 then along the road north then east to...
43,63 then north past Azure Watch to...
*46,39 then NE to...
50,29 then north to...
52,18 then west to...
37,21 then south to...
36,32 then back to 27,51

*Note: the roaming guard will kill this one.

The spawn time is very quick (15-20secs). Wait for the corpse to disappear, b/c you may get lucky and have the bandit respawn in the same location. The bandit will not despawn on his own.  He has to be killed to spawn at a new location, so camping one spot for him wont work.

If you have a mount the curcuit doesn't take very long.  I killed him 7 times before I got the mask, but only took like 30-45mins.