Por-15

[LeSabre in Buffalo]

LOL, I put 90k miles onto that LeSabre in the roughly 3.5 years I had it. About evenly spaced each year, too. The Cruze will likely be just under 28k miles on its first birthday. Work sucks...

$300 will have you set up nicely in the rust-repair department. That's 2 new rocker panel skins, enough POR-15 to last a loooong time (didn't use a full quart, even applying it very liberally), painting supplies, safety equipment such as earplugs/respirator/gloves/goggles/disposable long-sleeve shirt, and some new tools like an angle grinder and cutoff/grinding wheels.

POR-15 is some seriously nasty stuff. It reeks to high heaven when open, and being in close proximity to it for extended periods of time without safety gear is highly discouraged. Make sure the respirator is organic vapor rated, since your head will be nearby where you're painting it for a long time. And, if it gets onto your hands, forget about getting it off for a week or so. I thought I was going overboard on with quantity and use of safety gear. It ended up being just enough, and used enough to keep some potentially serious injuries from happening.

The other benefit of geeking out in safety gear before working on the car was I could work on it far more comfortably, and wasn't distracted by fumes or sparks as much. Instead of getting sick on paint fumes or dust from grinding down rust, the respirator let me breathe pretty normally without being sick after painting or grinding. The gloves kept sparks/paint from my hands, and gave a better grip on tools than sweaty, filthy hands. Ditto the goggles for my eyes. More than a few pieces of rust were deflected away by the safety goggles.

Be safe. You can always replace panels or an entire car. You can't replace your health.

[MattStrike]

Also note: If you decide to weld the panel in (I would), be aware that the car sheet metal is coated and galvanized. Welding on galvanized (un-prepped) steel is bad: The fumes are hazardous. At each weld point, use a flap sander or sand blaster to prep the steel. Welding will be much easier with no fumes or fluffy white stuff hanging around your welds. If there is an area that you can't properly remove all coatings, heat it up with a torch first (paint is flammable even when dry, so keep that in mind) and make sure you ventilate the area with fresh air!

[LeSabre in Buffalo]

Good point, and another reason to wear an organic vapor-rated respirator. Getting overcome by fumes is a quick way to ruin one's day!

[Grimm]

I've never used either product, but I have an article in a Auto Restorer magazine somewhere from several years ago where they compared POR-15 against Eastwood's rust inhibitor. The Eastwood product came out on top. They used both on a rusty hood and left it sitting outside for like a year. They divided the hood into three sections, with an untouched area in the middle. I think I remember from the article, it said the rust crept into the POR-15 side, but not the Eastwood side. I think the Eastwood product was also easier to apply. But again, this article was at least five years ago, so products may have been improved/changed.

[Roadrunner]

I used the Eastwood stuff on my 93 for ease of application and convenience - they sell smaller quantities and spray cans. You can also paint over it.
It has held up much better than I expected.