Approach the bridge near Lucan's Mount from the west and walk the bridge ( 100, -47, -660 ) /waypoint 100, -47, -660
NOTE: This is a tedious step. Go slowly, walking to the other end of the bridge.
Any time you see a beetle ahead of you, use the broom you were given to repel the beetles that appear on the bridge. You can set a hotkey to click the broom to make sweeping easier. Beetle pathing is highly variable; you may end up repeating this step several times until you cross the bridge without murdering innocent lives. Don't let a beetle cross your path. Stopping until the beetles moves past you will still kill the beetle.