The best way to "true" the bar rails is with a bar grinder. As you probably don't have one, the next best thing is a 12 inch woodworking sanding machine with a 90 degree table. Use a coarse paper with hard grit. Just run the bar past the disk smoothly, and the rails will quickly both be the same height and exactly 90 degrees to the bar. Look for nice even material "machining" along the length.
I don't worry about burning etc. If the rails true with enough depth for the tangs, then they work fine. File off the burrs on the edges with a flat file held against the bar. If the rails are spread, you may need to use a bar-closer to get them true.
Filing down badly uneven rails is really difficult on high quality bars as the steel is very hard. Grinding (or using a sander as a grinder) is really your only option except for light work or touch-ups. If you do file, use a machinist square to check the evenness of the rails all the way along the bar. Unless you are doing a lot of boring, don't worry about uneven wear around the tip. It hard to get them true anyhow as the sprocket gets in the way.
