Yes, treat them separately. Aluminum is a "hot" metal (much more chemically reactive). I have a commercial sonic cleaner and it really does make things squeaky clean, although I live in the Fascist State of California so I have never cleaned a "can".
For the Aluminum I would use non-acidic detergent (Simple Green, Dawn, maybe. Something low sudsing. Keep an eye on it for sudsing and experiment. Avoid dishwasher machine detergent.
For steel, I would add something acidic such as vinegar, lemon juice, Lemi Shine or some commercial stuff made for sonic cleaners (I have some sold by Lyman).
Be aware when cleaning brass if you have something copper (such as a penny) in the batch it will turn your brass pink. (Don't ask me how I know
) But then, pink brass might help you separate your brass from other people's brass at the range, LOL!
Do not put flammable chemicals in your sonic cleaner. I have heard that you can put parts in a sealed jar (or freezer bag) with paint thinner and submerge the jar in water in your sonic cleaner, but I haven't yet tried it. If you try it, do so outside in a fire safe area and wear protection.