To me, Gunk and similar products leave an odor that I don't like. I have used Purple Power with some success. It doesn't leave an after-smell. If the engine isn't too horrible, even Simple Green works pretty well. Remember, whatever you use, do NOT let it dry on before rinsing. Good Luck
But the real key to a good cleaning is the water pressure. Get, borrow, steal, etc. a good pressure washer or those "do it yourself" car washes with the wand will do a great job. The average garden hose & nozzle won't cut it.
Simple Green or Purple Power and a few good brushes. Stiff bristle bottle brush to get into the hard to reach areas and a good deck brush for everything else.
Start up the car and let the engine get slightly warm but not hot. Cover your alternator and distributor to keep water out. I like to use plastic food wrap since it clings well and will form to whatever accessory you're covering giving you access to the parts you want to get clean. Disconnect the battery cables. Work in specific areas and don't forget about cleaning up the engine bay walls and surrounding area. A clean engine with a dirty bay is counterproductive in my book.
Spray down the area you're going to work on and try and loosen as much of the caked on grease and sludge that you can. You'll want to rinse it at least a few times to wash away the sludge and get a clear view of what is left to do or any spots you may have missed. Do this throughout the engine bay.
Once you're happy with the cleaning job dress the rubber with whatever you like to use for rubber. I like using Mequiars Tire and Trim gel. Keeps hoses looking fresh.