Swamped

If there isn't a hole in their patrols then you'll have to make one. This is why you took some armor from the marshguards you tied up.
However, you don't know of any one armed marshguards and none of the three were Walter's size.

Dean and Jackson though can pass for guards easily enough - at least for a short while.

Have the two chase you, calling to the marshguards for help. Then lead them into Walter's wrestly arms.

Oh! Also rope traps!