As stated in the cleaning your buggy section, GT85 is used on the metal and bearings of your buggy to keep the rust away.
For the transmitter, in the rain, and cold of winter, a transmitter muff is a great investment to protect your expensive transmitter.
To set your buggy up for the wet, in general, more toe in at the rear is used. We use lighter shock oil, and use softer tyres along with raising the ride height to induce more roll in the setup.
