I will report on my experiment to the (bitter?) end, for the enjoyment (?) of those that are interested.
I got the U-Pol Acid#8 (Thanks again E2V!) etch primer.
Sanded.
Degreased.
Primed the props and their hubs with the spray can.
Primed portholes and bollards and drop stoppers by brush.
The portholes were glued on already, so I couldn't sand them (or wouldn't, rather).
The drop stoppers above the doors are of copper. They were sanded, but still the primer didn't adhere well. Maybe, when the etching kicks in it does.
I learned from the source that Stan posted (thanks, Stan!) that etching will happen after the primer has dried. Although the instructions of the product that I use say that curing will take place in less than 20 minutes, i found it takes longer than that. I may have had unnecessarily thick coats (according to instructions, 2 coats would be ok). But indeed, when dried, the primer has stuck pretty well.
The primer seems to stick