Use Prolan Extreme under the chassis, engine bay and under the deck. For the cosmetic surfaces, such as the bonnet and mudguards or areas that are in human contact, spray and buff in with a soft rag. This will leave a wax finish.
Prolan will protect the dead corners under the deck against corrosion where the cut grass is not polishing the steelwork.
The time between recoats depends on the situation. However, when washing, look for the water beading up. If it doesn’t, it’s time to apply another coat.