There's no way sanding can get to the bottom of rust pits to clean them out, short of sanding the whole thing to paper thin. At that point you might as well replace the whole hood.
An alternative to sandblasting (agree with Fox on being careful doing that), would be to build a dam out of modeling clay around the affected area and soak it with something like Evaporust to remove the rust, then clean it and paint with epoxy primer, then fill and paint. There's a possibility the Evaporust will disappear thru pits that are deep enough, but it is more gentle than sandblasting.
