How to access the high 3rd brake light wiring to install an inline flash/strobe module? 2018 Equinox

[Saltycracker]

I attempted this once and couldn't get it done. How to access the high 3rd brake light wiring to install an inline brake light flash/strobe module? 2018 Equinox. The 3rd high mount LED brake light is enclosed in the rear roof spoiler and I am just trying to find a way to access the 3rd brake light wiring to install the 3rd brake light flash/strobe module. If anyone has had success doing this please respond. I installed a 3rd brake light flash/strobe module on my wife's 2014 Chevy Captiva Sport with ease after it was rear ended and repaired. Also added a flash/strobe to my motorcycle brake light.