the "string line" mix question

when "EQ"ing is it best or at least common procedure to apply EQ to individual tracks or to the final mix or both?

You try to get individual tracks to sit with each other initially, and that invariably means track EQ. But it's not at all uncommon to find that you can make an overall result smoother with the odd slope change here and there.

I'd say though that you should only be making very low Q changes at the final mix stage - it's the overall shape you might want to alter, or the shape of things like overall reverb EQ. If you find that you are wanting to make more incisive changes at this stage, then the basic mix almost certainly needs revisiting.