Just doing a '68 coupe. Red oxide the complete underside, interior, front apron outers, and all of the rear wheel wells.
Front aprons get seam sealer, and sound deadener with a quick spray for and aft of the shock towers but not in the mounting well where the UCA goes.
Black will go over the engine bay and aprons, sprayed down into the tunnel, a feathered edge wherever the gun can get to from leaning into the engine bay while spraying the firewall. Whatever overspray goes onto the mounts for LCA, strut rods, underside etc. will be whatever it is.
Rear wheel wells will get a total coating of deadener, then body overspray wherever it goes.
Overspray under the car wherever it goes as the sills/rockers are painted. Then pinch weld blackouts.
Think the result will look good and be "similar" to original.