Imron was what DuPont called their polyurethane industrial paint. It's tough as nails but not the only tough paint out there. A friend, way back around 1977 painted his project Nova with Imron, and it looked really sharp. However, it can be hard to spray because it's so thick - often requiring heating up to thin it. The same reason that makes it touch also makes it more likely to get orange peel. And it's generally available in industrial colours only; if you want to paint your Coca-Cola fleet, or BNSF locomotive, they'll have your colour but don't go looking for something to match up your vintage Charger or 1980 Dodge pick-up. Around 70% of new semi trucks are using Imron from the factory, and they likely get the 55 gallon drums. The Imron mixing system is very expensive, most jobbers would lose money with it unless they supply a major truck or light aircraft paint shop. As with all isocyanate paints, you need a good respirator with supplied air.
You are correct on the Iscocyanates. Today, it's a Xalta(formerly DuPont) product. I use it a lot and just as any paint, the more practice, the better you learn the characteristics.
Typically I use 3.5HG, 9T100A and M32 Thinner with accelerator most of the time. I can make it flow like glass.
Fyi, you can actually brush and roll it with an additive for those who may want to refinish a trunk or paint a floor without all the masking and overspray.
It is very hard and I wouldn't ask my worst enemy to cut and polish it as it's very hard after the first 24-48 hours.
Black or white averages $80per gal, $42 2qt of hardener (4:1) with Thinner, under $200 per sprayable gallon. Corlar epoxy primer is used on all steel surfaces and polyester filler and primers on top with urethane primer prior to finish application.
It does hide a lot of sins that BCCC will reveal as in marginal bodywork due to the mil thickness.
One of my favorite OEM looking finishes was using the old Centari system(discontinued) with basecoat hardener and Urethane clearcoat.
I've used Imron on amusement rides, race cars, roll cages, trailers, football/baseball helmets(yes,it holds up to impacts), caskets......it's very versatile.
I gotta add, if you have projects with good, well prepped steel there is also a DTM version of Imron that I've used on trailers, tube chassis subframes and connectors that works flawlessly and wears like iron.