The ornamental design for a brush, as shown and described.
FIG. 1 is a front perspective view of a brush showing my new design with a
cover to be cleaned shown above it, the cover being shown in broken lines
for illustrative purposes only and forming no part of the claimed design;
FIG. 2 is is a rear view thereof;
FIG. 3 is a side view thereof, the opposite side being identical thereto;