I have used gutter guard on the few grilles I have done, but when doing a bigger project like my wifes grille, I used Stucco reinforcement mesh. It comes in big sheets of 3x6 or something like that and only cost like 3 bucks. It's seems pretty weak as a whole sheet, but once cut down to size it about the same as gutter guard. It has a little bit different look than gutter guard too.
