How to handle - Floor surface rust

[shifty]

Shy of replacing the foam gasket on the fresh air intake of my GMT400, I fixed all water leaks in my truck. Now I need to clean up the damage of PO ignoring them.

I'm installing tar-like adhesive-backed sound deadening mat (Dynamat) on my cab floor, but I want to deal with some rust first.

What's the best way to handle these bubbled up and surface-rusted spots before installing the mat?

Sand, self-etch prime or rust bullet/POR15/similar rust sealer? Paint over that?

How long should I wait after treating and paint before installing the mat?

Any "aha!" things I should know about, like the rust at the seam sealer up front?

Feedback is appreciated. Looking to get this started soon.

Pics, hopefully the forum doesn't make them too "potato" quality, if it does, I'll post better close-ups later today. (edit: Yup, it potato'd them out, I'll post better hi-res pics in a few hours)