Create keyboard shortcuts for touch bar's functions
Karabiner was created for this. It'll allow you to create a layer for your volume toggle and setting, brightness, play/pause, and everything else the function row or touch bar was able to provide - except, of course, the very custom programming some apps have the touch bar hew to. 

I primarily use Karabiner for my volume:

a: volume -
s: volume +
d: mute toggle