Over a period of time dirt will build up on anything, it just takes longer on a surface coated wtih F11. As soon as you wipe the dirt away and dry the surface, the F11 surface will quickly sheet off water again.Click to see full answer. Similarly, you may ask, how long does f11 last? 3-6 months how often do you apply top coat? Reapply a layer of clear topcoat every two to three days to prevent chipping and enhance shine. In this manner, is TopCoat f11 legit? F11 Wax Reviews 2020: TopCoat and their fantastic range of products. TopCoat has been one of the more popular go-to “exterior auto dealing” company for quite some time now. On the other hand, the TopCoat F11 is, by all means, a professional grade sealant.Can you wax over f11 TopCoat?You can keep the same guidelines for TopCoat® F11® like you would a wax when it comes to applying the product after a fresh paint job.