At wits end with hull red paint

MusicCity didn't explicitly state the reason why, but he's right about needing to apply a primer.

The problem is that the putty is absorbing paint (it's slightly porous). Primer should seal it right up.

I usually make sure that any dark or light areas are pretty well primed prior to the base color so that the color is pretty even. But, what's done is done. In your case, I *Think* what I would do is to spray a thin coat of red over the areas that are overly dark and try to lighten them a little in respect to everything else. Eventually, if you just keep adding coats, the difference will most likely go away but at the same time a bunch of coats isn't going to do much for any surface detail on the hull. It's times like this that an airbrush is so handy because you can spray such a finer area than with a can.

Also, try sitting your can in a pan of warm (NOT hot!) water prior to spraying. That will warm the paint and allow it to spray in a finer mist.