The video shows a recent model of an O27 turnout. The earlier ones (1121, 1122, 5122) often have the wires routed so that you do need to take off the bottom of the turnout to get to them. This involves drilling out several small rivets and the riveted end of the post on the bottom of the frog. The small rivets can be replaced by small machine screws. For the frog, drill and tap it all the way through the post and out the top of the frog, then reinstall it with a flathead machine screw short enough not to protrude out the top, whose head will neatly fit into the recess in the bottom plate.
He keeps stressing that the constant-voltage transformer must be in phase with the track voltage. He is wrong about this. Out-of-phase works just fine and can slightly reduce the voltage drop through the outside rails of the track and the wire feeding them.
He ignores the greatly increased danger of coil damage. The cure for that is to power the switch machine not from an AC source (phased or not), but from an electrolytic capacitor (about 5000 microfarads), recharged through a small lamp (53) from a DC source, or just through a single 1N400X diode from an AC source, to supply an entire layout.