Guys, it is very possible to do for anyone. The key is to keep out too much resistance in the connections, or the windows will be very slow to move.
I have almost finished my dual window controls. I had to tap into or modify every window wire basically. I had to add two relays per door to isolate my right hand control switch.
I'll help more later, but here are some basics. All window power comes from the blue/black wire in the LF door. All window ground goes through the black wire in the LF door.
The three other windows are powered by the red/blue wire, which gets power from the LF blue/black wire. There are six wires going from the LF door to the other windows, not counting the red/blue wire.
The auto down function is controlled by the GEM module. If you maintain the wire scheme like the LF door wiring, it will still work.
All of those wires are 14 gauge, barely large enough. The best thing you could do is to maintain as much of the factory wires as possible. Meaning remove the seats and rug, then reroute the factory wires to where you mount the master switch. So don't cut any of those wires, first route them to where they need to go, then deal with the connections.
I can say that crimping with butt connectors, and soldering those, will create too much resistance. I have all of mine done except the RF relays. I shall try to just crimp those connections, to see if that works better. I'll have to go back into the three finished doors, to improve some connections. Good luck all,