The most difficult part in installing the magnets is that they must be polarized the right way - and the little buggers want to snap out of your finger when they get near a magnet of the opposite polarity. One trick we found to get the polarity right was to use a felt tip to mark the same pole of each magnet before you install them - then peal them off the polarized "stack" one at a time as you put them on the drywall screws . As you can see in the photo one of the parallel rows has been marked black, the opposite row is unmarked. We didn't bother super gluing the magnets to the screw heads as the magnetic attraction and diluted white ballast glue holds them in place. I've included photos of the interchange tracks after ballasting over the magnets. The train crew found it easy to positioning cars over the magnets using the weed as a locator.
