I've used SEM Rust Mort and the directions state;
APPLICATION:
BRUSHING:
Apply multiple coats, keeping the area wet with Rust Mort until all rust is converted or removed. The longer the
surface is kept wet, the better the final result. After completion, remove any excess or non-converted Rust Mort
by rinsing with water and a brush. Make certain all surfaces are completely dry before proceeding with body filler
or primer per manufacturer’s recommendations. Failure to remove excess material can result in loss of adhesion of
subsequent top coats. Limit exposure after drying the surface to eliminate flash rust.
https://semproducts.com/public/content/techsheets/sem_tds_rust-mort.pdf
So yeah, you have to keep these products wet, at least the stuff I'm familiar with. It's that or completely submerge it. Rust Mort works well, but it's strong enough to etch into concrete if left unchecked. You have to neutralize Rust Mort.
I’d never argue with the Jeep Guru ! He is called a wizard for a reason , man knows his shit to the tea.