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.
The little bit of grime and salt that the fluid film will hold is no big deal. I too give it a good pressure wash in the spring and start over in the fall, that strategy works great.
Now, I must warm you. I don't know what year your truck is but Fluid film will majorly soften the black coating GM uses on their frames. I use fluid film on my Silverado too but I do not get it on the black frame. Again, DO NOT PUT IT ON THE BLACK FRAME! Everywhere else is fine but avoid the black waxy coating, if your truck still has it. If your black frame coating is curling or peeling than a very light coat of fluid film may actually soften it and make it repair itself but otherwise, I wouldn't get it on the black frame.