It's actually called fluid film Automotive - Fluid Film - https://www.fluid-film.com/automotive-applications/
It's not a one and done type of thing, need to apply annually. Overly simplistic description is that you're basically coating your bits in a layer of wax that apparently has properties...
I’ve got the same truck, also bought mine from MN last July. I have the sunroof and roof rack tho.
I didn’t bother with brushing anything before having the chassis fluid filmed. You got a good price and doing the work yourself is saving tons of cash. My sons still several years away from...