stripping a patina Duster hood

Don't get too aggressive trying to grind out every little pit- the heat generated grinding on that big flat expanse of metal can cause all sorts of warpage, rippling and distortion. Work slowly.
If you don't get it all, soak some rags in vinegar or Evaporust and lay them on the areas for a day or so, a little plastic sheeting over the rags helps keep them from drying out. Thoroughly neutralize afterward, seal it and follow with high build to get it right.