I did just my doors and used Resisto (something roofers use). It wasn't a hard job, but it's difficult to remove all the hardware from the door without leaving a small mark (like on those round caps when you're trying to pop 'em off). I noticed a bit of difference maybe ... don't know if I'd do it again as it does add a few pounds to the cars weight and the difference wasn't like 'night & day' or anything.

Black 98.5 SVT w/ KKM intake, 73mm MAF, ASP pulley, Optimized stock Y-Pipe, 24mm hollow rear sway bar, Magnaflow resonator, Magnaflow mufflers, Roush springs, KYB struts