Wouldn't it be easier to just put some light pressure on your break pedal while you're engine breaking? My older Acura definitely lights up the break lights well before actually engaging the brakes.
Much easier, but not as technically interesting :)
And I do pedal it if I think the driver behind me is risky, though I'm not sure where the light engagement is relative to brake engagement.
That foot is on the gas pedal still in a lot of cases