I do it for myself and friends- it's a lot of work. To me undercoating means rubberized undercoat which is a waste of time. Anti corrosion spray is underbody and inside body panels- I drill a few holes for access to the rockers. For the price of a new vehicle and I tend to hold on to them- I do it and clean the drain holes. Every year is too much- 5 gallons of No drip here is $200.