I would not use "any old silicone" on the metal parts either. It might be incompatible with the O-rings, both the visible ones and the ones hidden inside the button and shaft holes of the housing.
If you want to keep your Aquatica (or any other) housing in pristine condition, I recommend the following:
Soak and rinse your housing after every dive even if you did not dive in salt water. Soak the housing for atleast half an hour in fresh water. In the beginning, at the middle and at the end, remember to operate all the pushbuttons, knobs and levers. The idea is to get rid of any sand grit, fine silt and salt water/crystals. I can tell that these cumulate in the various holes if you do not rinse the housing properly.
Take care of the main and dome port O-rings according to manufacturer's instructions. You should regularly observe the condition of the O-rings for any signs of decay, softening/hardening, cracks or other flaws and replace these O-rings when needed.
Unless you are really confident in DIY fine mechanics, be prepared to send the housing to a proper service center for a complete overhaul and replacing of all internal O-rings if you are experiencing repeatedly jamming or excessive friction of any of the controls. From a risk management perspective, it is better to replace the internal O-rings before they leak.