How to clean up after a grease fire?
This is no big deal. Small grease fires happen constantly in commercial kitchens. Ever see a big flame coming from a wok at a good Chinese restaurant? That's probably an oil flare up, not alcohol, and is one of the things that gives a well-made stir-fry its trademark smokey flavor. Most of the time, in between uses, commercial woks just get cleaned out with some water and a stiff bristled brush.

As far as your cast iron goes, unless you let it burn for a while, you should be able to clean it the way you normally would. Give it a good wipe with a dry towel after to get any black bits out so they don't stick to your next meal. People way over think the care of cast iron pans.

As far as your cabinets are concerned, if it is actually soot and not temperature damage to the material, you just need a basic degreaser. Most kitchen/all-purpose cleaners are degreasers. This one is my favorite for non-food-contact surfaces, such as cabinets, if you're interested. For slight graying from a bit of burnt oil, a good quality glass cleaner would probably do the trick with minimal effort. If you end up needing something beefier, check your local grocery store for Lestoil. I have never, ever encountered a greasy soot will stand up to that stuff. It's rarely my first choice, however, because it's got a very strong, distinct, (though not entirely unpleasant) odor. If for some reason, you've got the world's worst grease stain and absolutely nothing else is working, and you'll have to replace the surface if you can't get something to remove it, lye will get rid of it. Lye is also extremely toxic, gives nasty chemical burns on contact and in my opinion should only be used as a last resort. You can buy pure lye, or spray on lye-containing mixtures in the form of oven cleaner. Note: this has a much higher chance of totally destroying the surface you're attempting to clean than any other method. (as an aside, lye is a great way of stripping old crap off of cast iron pans)