The ornamental design for a paintbrushprotectivecover, as shown and described.
FIG. 1 is a side view of the paintbrush protective cover within an environment.
FIG. 2 is a right side view thereof.
FIG. 3 is a left side view thereof.
FIG. 4 is a top view thereof.
FIG. 5 is a front view thereof; and,
FIG. 6 is a rear view thereof.
The broken lines in FIGS. 1-6 represent unclaimed boundaries of the design. FIG. 1 further includes a paintbrush shown in broken lines for environmental purposes only, and the paintbrush forms no part of the claimed design.