Lots of ways, depending on your preferences.
For fast and easy, sandblasting is probably tops. Especially if you pay someone to do it for you. I think the best way is to have the entire car disassembled and take it to get blasted. But if you're just doing the engine compartment, it doesn't seem like that great of an idea to me. The sand gets everywhere.
After that, chemical stripper does a lot of work for you and speeds up the job.
I see where a lot of people here use a wire wheel or sandpaper discs. The posts I have read seem like it was a lot of work and time spent.
I'm not sure of other options. Probably start with stripper, then clean up the rest with a wire wheel.