Blowing scuba tank air (its super dry) into the housing from a tank or reg works well in a pinch.
Closing the housing an an AC or dehumidified space helps, and don't have any water on your hands while doing it!
Sometimes the condensation will go away after the housing and camera have time to come to equal temperature with the water, so pre-chilling the camera in water before a dive can help.
Yes the silica gel packets work. You can even use the free ones that come in some packaging. Silica gel packs can be reused/recharged by gently warming them in an oven, microwave, or other warm/dry place like on a radiator or in the hot sun. Look up the temp to use, can't remember off the top of my head. Don't overcook them. Microwaving takes a long time at low power. Oven needs a low temp. Consider a dedicated non-food oven.