Juno Park here. Here are some tips for riding your motorcycle in the rain. Keep in mind, like the apparel that you wear when riding at night still apply for low visibility conditions like riding in the rain. You want to make sure that your gear has retro-reflective materials as well as bright and noticeable colors.
Of course, having waterproof gear helps keep you comfortable and focused and goes hand in hand. If you're focused on your motorcycle you're safe. If you're wet, cold, uncomfortable, and you cannot focus, you cannot concentrate on your ride and maintain your safety.
As far as riding techniques go, make sure that when riding in the rain behind other vehicles, try to position yourself in your lane to ride behind the tire tracks. The cars in front of you have already pushed that water aside and you will gain more traction when riding within those tread tracks.
If you are encountering a big puddle, try to slow down as much as possible. And if you can, if conditions permit, squeeze in your clutch and coast through larger puddles. If you find yourself on the highway at higher speed conditions, try to maintain your speed and avoid abrupt changes as abrupt changes in speed will tax the traction of your tires. You want to try to maintain as solid of a contact patch of the tires to the road as possible.
Again, keep your eyes up. Avoid looking and focusing at hazards. Sight your path as far ahead as possible. Don't fret. Your tires still have the majority of traction in the wet. What you want to try to avoid, again, is abrupt changes in speed. So try to keep your braking smooth and try not to be heavy handed on the throttle.