Before you use your Giant English Wheel Idea
You need to determined why the high spots are moving all over the hood. You can spread fillers and skim coats all day long for seven days and seven nights and block and block. But you are not going to get what you want until you analysis what is going on with the metal. If you can't slap or dolly the highs down without chasing them all over - then best guess is stretched metal. It's hard to give any suggestions that could help you with your problem without seeing it first hand. If you are not sure what you are dealing with try to find someone who can help you figure out what the,.....is going on. Hoods are difficult, but as already suggested the right tool (either hand sanding board
or a straight-line airboard) will help knock the highs without digging into the lows). Use a criss-cross sanding technique all the way up to the center of the hood that way you keep from creating a trough; if that's what is happening.