I know there's been plenty of threads on rust issues, but I'm just looking to see if I can stop this rust from advancing by spray painting... I was wondering if it's a good idea to scrape of some of the surface rust then spray some of this on krylon rust fix
Then just spray on some rust preventative spray paint after.
Then I got the idea to rub a good amount of wax on top of that to repel water.

Would this work? Or is there a better way such as sanding it down to bare metal, prime, then paint?

This is the bottom of the inside driver's side door (passenger side is less rusty):

 

I ouwld drill a smal hole or three to keep it from trapping water in there. Brush off as much rust as poosible and use a good rust restorer. Can' recal the name of the best one, but would recognize if I saw it.....someone else will know...

Paint over the restorer, and do not worry about wax really.. mainley seal metal from exposure to moisture is the key, and of course any salt.

That does look pretty bad, but maye salvageable.

 

Remove the interior door panels and vacuum and blow out as much of the crap inside that you can. Then a wire wheel on a drill and some por15 and paint on the outside. Then, after it's all dry , pour some motor oil inside the door, it will never rust. Clean it out every 6 months and put some more oil inside.

 

Just ordered some POR 15 today.
I bought the $21 black por 15 starter kit, and used a free shipping coupon I found online This is the "key code" I used anyone wants to know: PNfSO ...saved me $7
So I guess I'll just wire brush the rust off, use marine clean, then "prep & ready", brush on some POR 15 and stare at it for a while, then apply the second coat. I don't think I'm gonna use a topcoat since you can't even see the bottom of the doors and they're not in direct sunlight.

And thanks for the suggestion zman with the removing of the panel and doing the whole door, but that's just a little too involved for me lol. Just looking make it so my doors don't rust through all the way to the exterior. I'm not really too worried even if it does... It'll be a mudding/trail truck later in its life so it'll get beat up anyway.

I'm gonna hold off on the motor oil as well. I don't think the 01 models came with a crankshaft and pistons inside the door panel like yours

 

Here's the before & after with the POR 15, no topcoat. I just painted whatever was rusty and not the whole bottom of the door, I was too lazy. Only got pics of the drivers side. Both doors were this rusty from one side to the other. Hopefully it'll hold up for a while.