Hate that! You buy a car that looks solid, then a few months later rust bubbles appear. Take a grinder to 'em and--sure enough--there's a bigger problem than you thought.
That's what happened to our budget-built Duster. We initially took it to Car-Nation Auto Body hoping for a minor repair to the lower edges of the quarter panels. The guys at Car-Nation broke the news that: 1) The rust needed to be cut out to fix it; 2) By the time we repair that area, we might as well fix the door-dings in the quarters; and 3) If we have to match-paint the quarters, they're not going to look the same as the 30-year-old paint on the rest of the car. So, you guessed it--the Duster's getting painted.
But for now, have a look at how to fix mild quarter rot the easy way. The techniques shown aren't for hard-core rust-belt Swiss cheese or full-on show cars, but you can probably do them yourself if you have the right tools--in this story, "the right tools" means air tools, many of which may not be in the arsenal of the backyard dude. However, bodywork is very painstaking and much patience is required. In our experience, patience runs way thin when using hand tools, so the investment in a compressor and air tools is way worth it.