As a rule I use a lightweight focussing cloth which had belonged to a mate I used to work with. He died about 10 years ago and so it does double duty as a memento. It is black cloth on one side and red on the other so that there is a visibility factor when working where there are people.
I also have two huge weighted black and whit 'horseblanket' cloths but they are hot and heavy so seldom get used for their true purpose. The older, tattier one, covers the gear in the back of my van to keep it from view.
I also have the binocular viewer for the Sinar and a reflex finder for the Sinar. The bino-viewer lets you work a whole lot more aware of your surrounding when you are in busy public spaces. (As an architectural photographer I often shoot in busy spaces. The reflex thing is good for low- or high-angle shots and for shooting in plan mode for copying, for instance. Many shooters unfamiliar with ground-glass viewing often use the reflex because it provides a right-side-up view.
But for me, nothing beats actually immersing myself into the image on the screen with a 6x loupe under the black and red cloth.
"Photography was not a bastard left by science on the doorstep of art, but a legitimate child of the Western pictorial tradition." —Robert Galassi