Go to Wal-Mart and get a few cans of their foaming engine cleaner, apply liberally to the coated areas including the under-hood insulation. Just try to keep off exterior painted areas as it can make some waxes go milky if let sit. Let sit for 5 - 10 minutes then hose off with a medium spray from a garden nozzle until the water runs off clear. Any smoking you get will be from whatever didn't come off the manifolds and that won't last long.

I've been using that engine cleaner a lot as it's basically the same stuff as Gunk Engine Brite, and isn't particularly harsh and a very good general degreaser. As much as I've been using it on my diesels it's good stuff!

Next time you take the oil cap or anything else off that needs put-back, just place it somewhere really obvious. Like in a plastic pan in your driver's seat.