Ok, so not as bad as putting diesel in a petrol engine - but close!

Yesterday, when checking my oil level and dipstick, I got sidetracked for a moment and then forgot to put the oil cap back on.

I drove the car (X5 4.4) about 15 miles and then back home only to look under the hood to see oil leaking everywhere and a bad burning smell.
I open the hood and instantly realized what I'd done as amazingly the oil cap was still there!
Today I lightly jet washed the engine and surrounding area, however, upon reving the engine smoke and a burning smell still seemed to come from the engine area.
From speaking to a guy in the local car supply shop he suggestted using an engine degreasant all around the engine bay and underneath the car.
Then rinse it all down.

He assured me that the burning smell and smoke was just the oil (which seemed to spray everywhere!) burning off and it would take several hours to settle down.

I guess the purpose of this question is to see if anyone else has experienced this and/or if anyone disagrees with the advise I've received?

Thanks in advance for any help!