take coil packs out clean em like you would anything else but I wouldnt dunk them in water... wet rag will do it...
I dont know about WD40, does that stuff actually dry?, its an oil, and when it heats up in there wouldnt it like bake on somewhat?
Im just guessin...
to clean the valley, I used an alloy acid and a scrubbing brush/toothbrush, just use some old spark plugs to fill the holes whilst cleaning, then wash the acid stuff out, I wish I could remember the name, its pink stuff and burns after alittle while on your skin but damn it cleans alloy great... that way there is no oils or grease crap left there and it looks like new... just dont get it on paintwork obviously or anything else for that matter...
Ive done this a few times, I get a little over meticulous when I start to clean... it can take days sometimes...