Remove the engine and radio tray. Give it a good wash, spray with GT85 and then wipe that off.
After racing I use a power jet washer to clean the buggy. Some people use the kitchen sink and some use the dishwasher, although it's recommended you ask before using the dishwasher as an angry woman is not a pleasant experience.
If it's been some time since the diff oils were changed then it's a good idea to change them whilst the car is stripped down. They maybe working fine, but the oil will get contaminated from general wear of the gears.