I can't remember who posted it now but someone used a mellon ball utinsil with the serated like edges. Looked like it do well. Try searching lung scraper.
When you are reaching in to remove the internal organs, you know how you have to wriggle your fingers waaaaay forward to sort of grasp the heart area? If, when you're going forward to do that, you make sure that your fingertips are plowing tightly against the inside of the ribcage, you can actually free the lungs whole and ahve them come out with the innards. Nothing TO scrape
(Kidneys still have to be scraped out, I use a spoon, sometimes the bowl end and sometimes the handle end)