Folks forget that one of the biggest glare problems with a Dob/esp. a truss type is not light shining down the tube at shallow angles, but instead bright sources coming into the focuser almost perpendicular to the tube, but parallel to the back of the focuser. I notice it this time of year as the brighter stars of Orion as well as Sirius are rising while I am still observing galaxies near the meridian. I have made a black back stop extension for the UTA on the opposite side of the focuser but have not worked out how to effectively attach and employ it in the field.
Another issue that arises is when some sort of light is shining on the back of the mirror. This happens mostly during outreach when either a ranger sets some sort of "shielded" lantern down somewhere behind the scope or if someone is using their phone or a flashlight to look at the base of the scope. Headlights will do it of course...
Mike mentioned grazing angles from the truss tubes. Intuitively, very little of the light that actually reflects off a truss pole actually hits the mirror and even then, it is off-axis so it is really only the scatter from this off-axis light that enters the eyepiece.
The bigger issue light essentially parallel to the focuser tube that sneaks by the secondary. Baffling is something I have been working on with my 16 inch Dobstuff for about 12 years. It's a single ring upper cage design and all is reasonably well if the skies are truly dark and there are no sources of artificial light. But this is not always the case and so this has been a project.
To baffle the upper tube, I eventually just built a full circle baffle that attached to the upper ring so it mimicks a double ring upper cage. Previously light would bounce off the poles and down the drawtube.
The focal plane sits back from the secondary about 14.5 inches, this lowers the eyepiece height and the focal plane is well illuminated because of the 4 inch secondary. This allows me to also baffle the focuser tube from stray light with a 42mm hole in the upper cage baffle.
The original mirror box also has a full circle baffle and the back is a plate so there is no path for light to enter from the rear.
Normally it's windy so a shroud is mostly a sail but I recently added a shroud and I will be seeing if it helps with scattered light. My thinking is that if the focuser and upper cage are properly baffled and the mirror box is properly baffled, the shroud does very little.
12 years ago:
Mirror box and upper cage baffles