A properly preped metal hood will hold filler that is pretty deep with out it craking out, how ever just smearing the dents with filler is no the best way to go a body hammer and a dolly would work the best to tap up the lows in the hood then smear some filler on it! You could always have somone paintless dent repair your hood espeacially if it already matches the car and the dents are not to deep!