There are a lot of basting brushes out there for saucing or glazing BBQ (for those folks that sauce). Pastry brushes, silicone brushes with wide "bristles", ones with small ones.
I don't like to see "brush marks" on the final result. What is your preference for the type of bush you use?
I seem to have best luck with the thinner bristle silicone brushes. (of course it also makes a difference WHEN you apply the glaze)