That is exactly why I like Fluid Film. If your not working in brake lines, frame areas, or body panels because they are filthy greasy (but not rusty), I call that success. My Silverado has a nice buildup of various products over the years that is nice to look at for protection, but messy to work on, and I like it that way. Too thin of a product and it seems to wash off too easily. I think Carwell increased their viscosity on the undercarriage spray to slow down washout, but their crack and crevice product is still thin for better coverage in enclosed areas. Atleast that is what I heard.
Originally Posted By: buck91
I have used both on my F150. I did the exposed underbody panels with HDMP, allowed it to fully dry and followed with FF in hidden areas and nooks/crannies.
I like the fact the HDMP dries to a dry film but I don't think its as cost effective as FF and will be going that route for the entire process in the future. Except, as already mentioned, in high wash areas.