Yes, whenever you paint you want to give the surface some tooth for the paint to cling to, and you also want to degrease it with a light wipe of something like lacquer thinner.
I don't suppose those (bell ends) are retrofittable? I'm thinking not, looks like they're held in place by the channel frames - I imagine PB meant the chokes now have them incorporated right out of the box. But those covered chokes sure look nice...