i just case matched mine today, and its not terribly hard. like allen said, use the gasket that comes with it to match to. put the gasket on, use a red sharpie to mark off the area to be removed. then snag a dremel with some hi speed cutting bits, and go to town. i kept mine on the low (1200 rpm i think) setting for most of it, and broke into about 1800 rpm if that just for a little bit. Remove just short of the red marks (just so you dont over cut, you'll take the rest out w/ files), then break out the sandpaper and files. File and make sure everything is smooth and gradually flows, from the stock inside to the now-ported outside. then some 300 sandpaper, and then some 600 and you have smooth matched transfers.
for my first time i dont think it came out bad. could be better, but is definitely good enough to work and will get the job done. removing the bulk of the material is the easy part, i think. then its just about how patient you are and how long you feel like filing and smoothing out... filing, and smoothing out.