Righto,
I believe (from sitting at a desk) the easiest way to bypas the black out switch is as follows
1. Isolate battery
2. Remove screws from black out switch plate
3. Pull out blackout switch (AKA pineapple switch) from the dash.
4. Remove 1 green purple wire from one side of the switch (pin 5 or 6)
5. Put the now free wire on other green and purple wire with the screw.
6. Tighten up both screws as you may want to put it back to original
7. Re-install pineapple switch and plate and connect batteries
8. Test brake lights in all 3 positions
This is effectively bypassing the blackout switch without running new wires, cutting original harness and very simple. Shouldn't take more than half an hour to do the hole job

(says the fat man sitting behind a computer)