I agree with Dan (Turkey Hollow RR) re the use of the Dremel flex attachment for cutting squarely. However, I decided not to re-invent 'the wheel' re the cutting tool. I bought Gargraves' recommended cutting wheels (Gyros 2" diameter, pkg of 2, item 93108) and the 1/8" mandrel (item 83985). Worth every penny. Still using the first cutting wheel after building the layout.
Also agree with Rod Miller re dressing. 10-15 seconds with a jewelers file...railhead tops, sides, faces...done. The wheel cut is clean enough that I've never had a problem getting the rail pins inserted...steel or plastic...or the 910-4 blade connectors.
Re using the cutting wheels and the flying sparks show: WEAR THOSE SAFETY GOGGLES, pal!!
KD