I have never used duplicolor, but I would follow their directions.
The baking lacquers from Brownell's require baking, I don't know about duplicolor, I have never seen it mentioned on their label.
The Alumahyde ll also available from Brownell's can be baked or air cured, but air curing takes at least a week, and in my experience, longer.
But it gives a excellent finish.
If you use a product close enough in color to the original finish, you could get away with just doing the receiver.
If you are going to sandblast it, I would do it before you do your final degreasing/cleaning