I started using a Rolleicord IV (circa 1953) for a bit of street with a short cable release as I found the release lever awkward to use. Looking down into the finder is a very different experience to lifting the camera to your eye. At the moment of exposure I look away from my scene and "click". I also have a Hass 500CM, but my God, the clatter it makes at the critical moment! The Rollei is whisper quiet. It also has an antique look about it and I'm sure people do not perceive any threat from it. It hangs down on an old leather strap and I use it in the leather case, thus it looks very period.
Squeezing the small cable release is very discreet as my hand is quite close to the camera and half hidden by the lens hood. I move away before winding on and retensioning the shutter so hopefully no-one can follow the sequence. Got some good shots with hardly anyone looking towards the camera. I have a Nikon F3 with a WLF and that's a good camera for discreet shooting with a 35mm f2 lens, well stopped down there's little need to focus and on auto the exposure is well taken care of. Rollei takes Ilford FP4 and F3 uses XP2 Super. Not bothered much about colour though used it for E6 in the past and have got thousands of tyrannies to sort through!