best way to address rust on lower, inner door

[YELOSNK]

I unfortunately have been slacking the last few years on keeping a watchful eye on the more hidden areas that develop rust and finally found this after seeing a slight orange stain on the passenger side rocker panel. It looks like (probably salty) water coming through the drain holes has sat on the llp where the metal bents and started rusting it out.

what can I do to halt the spread? Wire wheel and then por-15? I'd really like to get it now before it gets worse and spreads to the front side. suggestions greatly appreciated!

this is the passenger side. Driver's side has it, too, but it's much less severe.

 

[01yellercobra]

First step is to clean all the loose rust and paint away. If it's not too deep the POR-15 will. But if it's too the only thing you can do is cut and replace.

 

[YELOSNK]

should I try a wire brush on a drill, or is that too harsh and I should try a coarse sandpaper?