orvil,
the only real way to get rid of rust is to cut back to surrounding good metal and weld in new OR to replace the panel totally. anything else is a temporary repair to prolongue a journey to the scrapyard.
if the blisters are in the middle of a panel (away from edges & seams) then you can rub back, hammer the metal to a slight indent with a ball pein hammer, treat with jenolite and fill/spray.
if however it is near the edge then the problem is more difficult to deal with as you usually have 3 layers of rusty metal to deal with - the outer skin wrapped around the inner lip. you can't really bodge this bit otherwise the two panels will vibrate against each other and the hatch will lose its stiffness. you really need to cut away the rot and weld in a new lip and flange.
BTW - metallic light blue is a real pain to colour match and your eye will be drawn to it just as easily.
Scraping it back, treating and painting will only give you about 6 months before it blisters again.
Don't forget to waxoyl inside the panel afterwards but make sure you've primed the back of any filler first as the waxoyl can sometimes bleed through and discolour the repair.
