Some of this can/should be done via a CSS system like SASS/Compass. If you're littering overflow:auto into a dozen rules, SASS/Compass would probably help you immensely. When you eventually decide IE6 support isn't needed, flip a single variable and poof--those rules disappear.
You could extend this to a _shame.sass file too, of course.
I'll add another vote for SASS/Compass. That system has saved me tons of heartache and hair-rending (and I don't have the hair to spare). SASS makes it easier to organize your CSS than to leave it unorganized. It almost makes CSS fun.
You could extend this to a _shame.sass file too, of course.