Using FF as undercoating just about everywhere on my Silverado. I know SOP is to put on in warm weather, blast off and wash after winter, and apply again. However, I'm crawling under the truck and coating places that I guarantee I will never be able to get to with a pressure washer or car wash. At the same time, the FF will undoutedly collect grime and salt here. Question--Does anyone know for sure, can an old coat of FF with grime (and SALT) just be covered with a new coat of FF and still protect?? FF's website talks of sealing and self-healing, so surely this would work? If so, I likely won't mess with washing any of it before reapplying.