Yep, remove O-ring, clean it with lint-free cloth, re-lube it and put in 'food-safe' ziplock. Clean housing O-ring groove, with damp cloth, then wipe clean. Put bagged, lubed O-ring inside housing, and put inside another plastic bag to keep dust out. Before storage I'll leave the housing soaking for at least a few hours in warm water (shower temp), periodically pushing the buttons to try to dissolve salts on the button shaft. Normally I stay away from cotton swabs (ear buds) as they can leave fibers.
Before assembly, clean the O-ring groove again, pass the O-ring lightly through your fingers to 'massage' the old lube. (You shouldn't need to add any more lube). Your O-ring bag will slowly become coated with lube itself, so keep it to re-use. Take your time during assembly in a dust-free environment.
I normally assemble the housing, put it in a bucket of warm water again and cycle the buttons again to try to free any solidified minerals. Then leave it to cool off before doing the final assembly in a cool room or aircon office. This step is probably overkill but I hate sticky buttons.
As a general practice, before hitting the water I'll leave a bucket of water to sit in the sun to warm up so that it is ready for after my dive. By the second dive it's a good 40C which is nice and warm but not too hot. Raising the temperature of water greatly increases the chemical reactions involved in dissolving salts. Just don't get carried away with it. If it's too hot to put your hand in, it's too hot for your camera.