Glitch spot 1: Sprinting toward the upstairs (closed) door on the wall and tapping V to vault through. For reproducibility I typically have fists or gun drawn and am looking straight toward the wall.
Glitch spot 2: Same steps as 1 on the downstairs door.
Glitch spot 3: Outside the front door of camo left side of stairs. Crouch walk toward the stairs/building. Once the players body is in the stairs it is then possible to easily crouch walk into glitch spot 2 or through the left wall instead.