Ikelite has some specific instructions for their housings. One is never, ever use any type of liquid silicone on the buttons (I wouldn't do this on any housing, you want a lube that is solid at room temperature).
As for post-dive use, at the end of the dive day, I first dip (never leave in a communal barrel) the housing, then soak it. Do not be tempted to look at pix on the dive boat trip back, as the salt is making crystals that wear on the seals. Then, get back to shore, and gently wash off the housing (and your dive gear). I then soak the housing for at least an hour in a tub (might have to remove strobes). Then, swish it around in the tub. Better yet, take a turkey baster, or kids "nasal bulb" (aka snot remover), and blow water into the buttons on the housing, while in the tub. Finally, remove the housing from the tub, and gently dry it off. Be careful in using a towel on an acrylic port, as they can scratch (you can use Novus brand no. 1 and no. 2 acrylic polish to remove scratches, available on Amazon).
Finally, after the water droplets are off, carefully open the housing back. Make sure you have toweled off the edges of the housing, where the gasket is, as capillary action will hold water in that gap. A tisssue to the edge will suck out the water from this gap.
I then take the entire rig apart, including the ports. I carefully clean all gaskets on the ports, take a Q-tip and clean out the port grooves, inspect with a lighted magnifier (or under a very bright light with a magnifying glass), regrease the O-rings, and reassemble with the port selection for the next day. I never, ever change ports on a boat (unless a live-aboard), as that introduces way too many variables (and wet air into the housing) that are too easy to overlook (like a hair or sand speck in the gasket).
I don't ever store my rig with the O-rings in. A flat o-ring will leak as easily as one twisted or with a piece of trash in it. Also very important to "pull" the o-ring between your fingers when LIGHTLY lubricating. Too much silicone can "blow out" of the groove, so go easy on it.
Based on use of high pressure piping systems, I must respectfully disagree with the comments on silicone oil. Viscosity of the lubricant is very important on the o-rings, as well as being chemically compatible with what is in your rig. Stick with the manufacturer's recommendations, as they are telling you what works best (leaking housings from customers is bad for business!!).
I know the above may seem a bit overkill, but I haven't had a leak in over 5 years, since I started using this protocol.