Gary, your trains will probably run well even if you don't bother to turn on the power.
You're right about the rails all being soldered together, except, of course, where there are insulated joints. All of the bridges are removeable by simply sliding the rail joiners out of the way, though, so they're not soldered either - I did provide drops at those locations to allow soldering below the layout, but none have yet needed to be connected. The entire layout is a single block, with passing sidings and some spurs able to be isolated electrically. I may divided the layout into two or three blocks if I ever get that second level built, but that would only be necessary if I had regular operators to utilise that feature.
Due to the design of the layout and its planned operating scheme, any train which is moving must have a designated operator, so, for me, one block works fine.
There's about 200' of mainline in-service, with roughly another 65' to be added on the second level - that figure doesn't include passing sidings or double track, of course.
Depending on the controller used, I have run more than a dozen locos at a time, and also trains in excess of 70 cars, although neither would be the case in normal operations. Most trains will be one or two locos, and fairly short trains - passing sidings limit this to about a dozen cars, although the main purpose of most passing sidings here is simply as run-arounds, as almost all trains will need to perform switching duties at the towns through which they pass.
I
do have a bus wire of sorts (#14 wires) to connect all of the throttle jacks together, but they all connect to the track through those two wires shown.
As for the colour coding, you'll notice that the white wire is heavier than the red one - I only used it 'cause I ran out of the smaller red stuff.
Wayne
hock: I see even you could not escape the darkeness of the "model railroad electrician" cult. Man, if you had used the same color wire for both connections, I may have been impressed! 
