Getting spray paint/caked on gunk sour a chain shut within? I recently get a large rat coop from a friend. It had...

I recently get a large rat coop from a friend. It had some caked on gunk on it, it be cleaned (kind of) primed, spray painted, and then used again so it get more gunk on it. It's got layer of gunk, primer, spray paint, and more gunk on it. I'd like to use it if I can, but is at hand anyway to get the spray paint, and the gunk bad of it? I'd like to paint it a different color next to non-toxic paint but I dont want to paint over the crap that's already on it.
Answers:    kutzit...is a stripper...wash it first beside soap and water and a brush...when dry apply kutzit to a side..agree to it sit @ 15 minutes...works like a charm
paint remover from home depot lowes or wallmart