I have an outlet that the circuit branch terminates in (wire coming in and ending). I want to extend this wire along the wall to two new sconces. Access can not be gained from the floor above or below. How would you do this? Would you just cut a channel in the drywall (me 1/2" drywall and 1/2" plaster), insert the wire and patch? I maybe have 10' to go. What happens when you come to a 2x4?