The answer for standard sheathed electrical cable wiring. You basically 'slice' the insulation around the wiring. You will need to, however, use Joist Hangers.to hold the insulation up. DO tack it to the sub-floor (from below) w/the Kraft side, up. Then install the Joist Hangers.
RE: Knob and Post wiring, you have a LOT to consider here! It's a hazard! Talk to a Pro, or atleast have one visit the home. Ask around - Someone knows what to do. Perhaps re-wiring w/sheathed electrical cable is the answer. Perhaps moving the K & P is the answer.
My best to ya and hope this helps.
Jay J -Moderator
PS: God Bless America!