When my pans need to be burned out to get rid of any crust, I simply take them out to the backyard put them in the Weber kettle, and build a nice, hot briquette fire in them.
That usually does the chore.
If they are REALLY bad, I'll put a layer of coals down under the pan, then fill the pan with more.
And, if you want to get rid of grease in your pan without totally cleaning it out?
Coarse corn meal.
And, if you have things that are burned on that you want to scrape off? Don't use a metal spatula, go get yourself a cheap wood spatula at the local kitchen store.