So glad you asked, JRS.
Anyhoo, the ingredients you will need are: an old pot (I like to build sort of a pyramid with several so the pedal will be completely submerged in water), some boiling water, a 15mm open-ended wrench (I actually had to use a 16mm on this particular model), an older French bike that nobody cares about anymore, a rag, and some cooking spray. (You can use any lubricant, I just prefer to use cooking spray.)
Build a pyramid with your pots so pedal will be submerged
Add boiling water (please practice with cold water if you've never done this before)
Wait about 7 minutes
Remove pots and use wrench to remove pedal. (Please be sure to turn the wrench the correct way, otherwise you'll be there all day wondering why the pedal isn't coming off.)
Take rag and clean both pedal threads and crank threads, apply cooking spray to pedal threads and put back on the crank. Remove pedal again. (I do this several times, I want to make sure that I haven't somehow managed to melt the crank threads.)
What you are (hopefully) left with is removed rusty, crunchy old pedals, and cranks with nice clean threads.