Rotary dial. Then you can take a picture for the Photo Challenge thread.
Seriously, just get a bottle of Lestoil big enough to cover your aluminum parts. You can add hot water if you don't have enough Lestoil, but the stronger the solution the quicker it works. Use a plastic container big enough to hold 2 to 3 times the level of the covered parts because this will slowly foam up. A little plastic cleaning bucket or something works. Do this where there is good ventilation because it smells and I don't know what's in the fumes. Shouldn't be too harmful but it smells like a gas station bathroom that's been cleaned with Pinesol.
Dismantle whatever is going to be treated with the cleaner, place in bucket, and wait as it foams up. Check it after a few hours. I wouldn't go more than 4, 2 worked for my carb and other small parts I've done.
Wear vinyl gloves and rinse with running water. You can use a plastic toothbrush to get the slime off. Dry it and use WD40 or water displacing oil to get all the water out of the passages. It'll be soft and leave gray stains on your hands that washes off with soap and water. After a day or so that stops.
This will work on valves covers and any smaller aluminum parts.
Remember: Ventilation (outdoors is best) and rubber gloves (vinyl are best).