I am going through the same process on my truck right now. I didn't want to hose it off either because I didn't want to deal with the run-off. What I did was buy a couple of underbed storage boxes at Walmart, sprayed GUNK on the engine and then rinsed the engine off with those storage boxes underneath to catch the dirty water. That helped to minimize the mess in the garage.
I haven't scraped yet- that will be next, I guess.
Steve
