Just out of interest… I am going through the same procedure on my older Volvo SP-A 290 Drives.
There is not much original paint left so lots of bare metal..
Scraping and rubbing down all old paint then sanding fair.
Followed by 2 coats of Jawels 2K (2 part) Etch Primer for aluminum.
Then 2 coats of grey Inter-Protect epoxy primer.
As I am in seawater will finish with Trilux antifouling; first coat before the 2nd coat of Inter-Protect has fully cured.
I will report back end of next season.
Interestingly … have used Upol spray etch primer and Primocon (not the spray type) in the past and have noticed the beginnings of corrosion, mainly on the “H” frame. This indeed may be just coincidence given the age of the drives so no firm conclusion. The drives do not have the Triangular anodes on the “H” drive, so this may be worth considering.