I ended up using zero rust, just clean everything up real good, don't worry about removing the rust, and paint (it encapsulates the rust). Removing everything from the dash area including speaker panel, cowl vent,(this will let out all your paint fumes) glovebox door etc. really opens this area up, also if your rewiring everything remove that too along with your duct tubing. This area was never painted originally (now you know why).
goodluck, and by all means when your painting behind/under there wear a respirator, and eye protection.