The ornamental design for a grillbrush, as shown and described.
FIG. 1 is a perspective view of a grill brush, showing my new design, said view being reduced to show an entire assembly in use;
FIG. 2 is an enlarged perspective view of FIG. 1;
FIG. 3 is a front elevation view of FIG. 2, the rear elevation view being a mirror image thereof;
FIG. 4 is a top plan view of FIG. 2;
FIG. 5 is a bottom plan view of FIG. 2;
FIG. 6 is a right elevation view of FIG. 2; and,
FIG. 7 is a left elevation view of FIG. 2.
The broken lines in the drawings depict portions of the grill brush that form no part of the claimed design. Note, the claimed solid lines consistently obscure the disclaimed broken lines for providing clarity.