I'll add to this old thread by posting a few photos from this summer's rust repair of the '99 Intrepid. The only rust was right below the gas filler. It was mostly bubbles until my son (it's his car now) scraped a stone wall and tore into the same area. The photos show the before, during (with different colors of filler) and after photos. The repair looked really good before I painted it, but I decided to paint it with a brush (because I had the right touch-up color). It was just too large an area to do with a brush for the white and the clear coat. It's not too bad for a 20-foot repair. I'm sure it won't last too long, but it will look better for a few years!
That looks pretty good! Yes, this shows that you can do acceptable "10 footer" bodywork on small rust areas at home (i.e. looks decent at those distances) if you remove all the rust, fill with layers of bondo (maybe with some reinforcing screen), sand smooth, prime and paint with a small can of custom mixed lacquer or enamel from an auto paint store and the inexpensive little spray cannisters and jar gizmo that they sell. The lacquer primer/paint/clear coat spray cans (e.g. Dupli-Color) from the regular auto parts stores will sometimes work OK too.
Be aware that any lacquer paint can bubble the adjacent existing factory enamel paint and make a mess that has to be sanded off and re-done. Lacquer can work IF you use many VERY light coats and allow them to fully dry in between - this can avoid the bubbling. Lacquer is easier to shine up with polishing compound than enamel. You do this after the paint coats (wash off all the polishing compound and dry thoroughly) and then top with clear coat and polish again.
The professional auto paint store can mix up a quart of either lacquer or enamel to exactly match your car's year & color of paint (and supply the matching type of primer and clear coat needed) . Especially with the enamel you have to use the multiple light coats to avoid drips which would have to be sanded out when dry, which is a big hassle. Unlike fast-drying lacquer, enamel can take many days to dry before you can sand any defects out. So lacquer is much more forgiving if you can avoid the bubbling. (Also safer if you accidentally breath any of it in.)
Just make sure with either type of paint to use a good filter mask like a 3M with two round organic vapor cartridges to not breath in the paint spray. The paint shop has these masks and cartridges, and some hardware stores have them. Also obviously wear safety goggles or glasses and an old baseball hat (the fine spray will drift into your hair). Some types of professional enamel are not safe to spray this way without a fully enclosed mask/breather set-up, so be sure to ask the paint store for an appropriate paint that you can use just with the 3M mask. Just tell the paint store guy/gal what you want to do; they are usually helpful to do-it-yourselfers (if not, just try another auto paint store).
When sanding the bondo and primer smooth with wet/dry auto sandpaper (working from course to fine grit), use the 3M cartridges made just for particles or the best 3M microfiber particles masks.
Again this isn't going to be a body-shop quality repair, but it can make the car look decent for around $100 in supplies and a little careful work. There are lots of books and on-line guides on how to to these basic body/paint fixes on small rust areas.