I find that one good coating a year gets me through the season no problem. I rinse my trucks undercarriage often, but only with a hose. Not with high pressure. I worry mostly about inside the frame rails and all the other inaccessible hidden areas of the undercarriage. Even if you use high pressure rinse it is not going to remove the Fluid Film in the rails and the hidden protected areas. I can always touch up the low hanging exposed areas in about 10 minutes. I do a full undercoating in the fall using the attachments that came with this Fluid Film Gun, and than I may do one or two quick touch-ups during the winter. I don't even clean the gun because the Fluid Film does not harden. Whenever I feel the need for a touch-up I just plug in the air and shoot it. I do the same with my trailers and machines. The Fluid Film in the gallons goes on a lot thicker than the spray cans in my opinion. I read on another forum that some guys were complaining that Fluid Film washes off easily, and it turns out that they were being sold the much thinner Fluid Film formula as an undercoating product. You have to be careful what you buy. I see sellers on Ebay all the time selling the thinner stuff. You can tell the difference by the color.