a few months ago i sanded and sprayed with rust kill all the little rust spots on my project car. (bottom of the dores and a bit on the flor.) but now it has sat for so long that it has all gone rusty lookin again. it has gone matt rather than the shinny rust look it is ment to have when using the rust killer. does this meen get out the grinder and start again (with a sanding disc of course)? or do you just paint over this as you would if it had just been sitting fr a few days?