When fixing a cracked grille (Duster sharktooth) do you "v" both sides of the crack or just one side? Also is it recommended to drill a small hole at the end of the crack to get it stop growing?

Yes drill the hole at each end, and be sure it's the end! Ving cracks will depend on where the repair is. In most cases where it's thin one side is enough, on thicker areas both sides works better, it's something that takes practice to get a feel for. Generally speaking roughing up the area on both sides (really rough, like 60 grit), grinding away bad spots, Ving the cracks, then PLENTY of finish body work will yield good results. The real work is what comes after the crack is fixed.