Use a soft-bristle brush or cloth to gently scrub the interior of the base. Sprinkle the cloth with more baking soda if there are stuck-on particles. Pour out the water, add some cool water to rinse, ...
If your car feels down on power, a trip to the garage might be in order, but checking these things before you go could save you a pile of cash.
Dealership rust protection costs $300-800 but worsens corrosion problems, while modern cars already have superior factory protection systems.