Welcome to the forum DmC. Optimum's position is that 1 coat, properly prepared for and applied, is all that's necessary. Adding more product assures complete coverage but does not increase protection or durability. Having said that, our approved installers are independent and have their own methods. It sounds like you're from Down Under, Joel Blake is the Optimum Master Distributor for Australia and one of the sharpest guys I know. You might contact him for advise - firstname.lastname@example.org.