I guess I approach this differently. If the car will see a lot of road time, I do not think I would go through the trouble a complete tear down, blast, paint. Leafs will rust simply due to design(friction).
If it will be a weekend cruiser show type car and you have plenty of time, then sure, put the elbow grease and time into it and it will last longer....maybe long as you ever want. If I were to go that route, I would try to find some Teflon type pads to put between each leaf to prevent as much friction as I could.
If a daily driver my vote we be clean them up good as you can, as a pack, then treat them or hit with POR 15 or Corroseal or some type of rust converter or preventer, then paint.
Corroseal seems to be pretty pliable where I have used it so I would think it would hold up well on springs. I have fought this on all of my leaf springs, once it starts, it will not stop. Rust looks nice an ugly on a lifted Superduty where you can see all the front spring pack(s).