Maybe I’m out of the loop, but what exactly is a “Trigor?” Do you mean a ‘turnout’, or a switch-track? If so, then I wouldn’t ballast under the turning points, especially if you’re laying your track on bare plywood.
Speaking of, have you installed any scenery yet on your bare plywood? I generally don’t ballast until I have the scenery base installed on any portion of track.
A Trigor is an older Walthers product which uses physical contact caused by a train passing over it to activate something–a signal, animation, whatever.
I s’pose you could glue a piece ov paper to the underside of the track, leaving an opening around the area where the contacts are. The ballast can then be applied to the track without it contacting the roadbed, and the track and ballast will be free to move up and down together with the weight of the passing train.