A bus wire will work. Rather than bisecting the layout, you may be better off having it loosely follow the design and curves of the layout itself, thereby minimizing the distance that your feeder wires from the bus to the track need to travel.
With Fastrack, you also don't need to use just the terminal sections to make your feeder connections. Almost all FT sections have two tabs underneath to which you can connect your feeder wires, such as by directly soldering to them or using the connectors shown below. Feeder wires can be 16 gauge.
As for connectors, there are "suitcase" connectors available; "T-tap" connectors; and "Wago" connectors, as well as others. Basically, a matter of personal preference.
You can also eliminate bus wires and use a distribution board, such as the 12 port one from MTH shown below. Simply run your transformer outputs to the red and black terminals and then run paired wires out from the other terminals on the board to the FT terminal wires or the underside of a FT section. You would generally try and mount the board under the layout in a central/middle of the layout location.
