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

It's so nice to not have to ride your brakes going downhill, especially when you also have to turn at the same time. (I miss my old manual car)

Newer manuals are really nice.. mine has hill hold, which some people hate but I enjoy. And supposedly engine braking uses no fuel.

Unless you have an older carbureted vehicle, engine braking should use no fuel:

https://en.wikipedia.org/wiki/Engine_braking#Limitations

Just do a decent job matching revs on the downshifts so you don't trade brake dust for clutch dust :)

Not all hill holds are created equal. On my car, the brakes release as soon as you start moving forward after hill hold, or after 1.8 seconds. On my friend's subaru, the brakes hold for 2 seconds period. That means if you can do a hill start in less than 2 seconds, you drag the brakes every time.

15 civic SI. Hill hold is 1.2 seconds I think and no early disengagement. But it's rear brakes only. You can't disable it that I know of.