Vehicle: 2011 Ford Ranger XL 2.3L (manual)

I've read many posts asking how to wire up the third brake and dome lights and read about as many different answers in the comments. I'm left wondering what my plan of attack should be.

The bed cap wiring (notice the brake light wires are BROWN and RED, which throws me off):



The harness (red, green, black, yellow) doesn't connect to anything but is fed into the driver brake light.

I've read it's necessary to run 18 gauge wire all the way to the cab and splice into the break switch. Haven't found much info on how to do that. The brake switch:




Beyond that, not sure what to wire the dome light to. I'm not great with electrical stuff, I was surprised I couldn't just splice into the brake light but many say it will cause the third brake light to blink.

I've also heard there is a 'secret green cable' sometimes under the spare tire and sometimes under the fuses in the engine bay for the third brake light. Not on my model...

Please advise if you can. Thanks.

 

Wiring the dome light to the brake light wire will only let the dome light come on when you apply the brakes.

 

Sure, I wasn't planning on wiring the dome to the brake light. My post refers to information suggesting that you should not wire the third brake light to the rear brakes either, because the blinker uses the same bulb and it will cause it to blink.
I'm wondering if it's really necessary to run wire all the way to the cab and splice the brake switch just to wire up the cap's third brake and dome.