I like DAP caulk, but actually all are about the same. I have found this to be pretty true.
Primer, I like Zinzer BIN or Sherwin's Primer. Both have never let me down.
Cleaning or striping. This depends on the surface condition. If its alligatoring, chiping, or surface imperfections, I would address those and scrape, sand, and prime, and fill in. But, if your existing surface is OK, but dirty, I would make sure its clean and dry before any paint hits the wall.
Now, the last question, this depends on how comfortable you feel doing all these tasks on a ladder and what your budget is. I do not do two story homes because of so many things to do at that height. Sanding,scraping, priming, and painting all require going up and down for that task then you move and start over.
Now, I bet you will find that renting a cherry picker and building scaffolding are about equal. A cherry picker would be safe, easy on the joints and very safe. I would not do this if the ground is soft as you will have ruts.
I rent these guys all the time and they are great. Carry your stuff, all your stuff, up once and then drive while lifted. "i would not recommend driving this machine while lifted especially on grass".