This is my first attempt at this so Im not sure of the process. I have a knife blank that I need to attach my scales to and a liner also. Should I epoxy the scales and liner both at the same time or attach the liners, wait for them to dry and then attach the scales.

liners to scale then scale to tang

Exactly. Tuskbuster is correct.

Impregnated liner materials often do not hold well with the epoxy unless you rough them up with fresh sandpaper and clean them with lacquer thinner of something similar.

Just my experience. You think they are stuck to the scales and then they pop off while shaping or drilling.
Tim

Thanks for the adivce. Rough them up with what grit paper?
Any suggestions for epoxy?

I usually use fresh 80 to 120 grit.
I really like the Devcon duel tube 2 ton epoxy.
Others post here of other stuff they like, but the Devcon has worked well enough that I haven't looked elsewhere.

Shape and finish the front of your scales(the portion closest to the blade) before gluing. It is next to impossible to clean those faces up afterwards.