In the hypershade for each shader, is a rollout for "Special Effects".
Roll that out, and you'll see "GLOW INTENSITY".
Check the docs for usage, as there are MANY ways to use it
PS - You can key it like any other attribute, by simply right-clicking the value, and choosing "Key Selected".
But seriously, check the docs, as there is a LOT more in there than most people think
Israel "Izzy" Long
Motion and Title Design for Broadcast-Film-DS