I don't remember how I did it before, when I added the required drivers to the Rescue CD disk. It must be done before burning. I don't find my way to any webpage where it is explained.
The same question goes also for adding the required keyboard files (belgian azerty-belgian-french) I made a working CD quite some time ago into which I managed to add those items, but I can't remember how or find instructions.Maybe changing keyboard layout has been included in today's procedure?
(I believe I created a new folder "Drivers" somewhere, OR maybe added my required folders/files to already existing folders into the location where current Reflect version is installed. But I'm not sure)
If you wish to make futher customisation to WindowsPE you would need to create a custom wim. This is beyond what we can support however here are a couple of links which may help.