I agree with the others,The time it will take for 1 conductor as opposed to a ckt.The same.
My experience: once you start messing with the K&T,you wind up replacing most of it anyway.

My thought would be,price out the material,then set a labor rate.

GFI,rarely work on a K&T setup,based on the way it is tapped hard to get all down stream covered with 1..If this route is taken,go with breakers.