Our zincs were eaten down to a scary level despite having checked them visually with our underwater camera a month ago. In addition, we hadn't known which type of anti-fouling to put on the aluminum saildrive and maxprop last year and so they had spent a year in the water without and the drive and prop had barnacles on them.
Before work but after high pressure wash and knocking off the barnacles:
We sanded the saildrive to the aluminum and put 5 coats of Primocon on it:
Then we put two coats of Trilux II anti-fouling on the saildrive, replaced the zincs, sanded the max prop and put 3 coats of Petit Barnacle Barrier on the prop.
Much better. We'll see how it lasts over the next year and whether we have barnacles growing at the next haulout.
During the process we found out that neither Primocon nor Trilux are legal in spray cans to sell in Canada. We had a partial can of Primocon which did the job and we had to buy the Trilux in a liquid paint form and ended up with a large enough can that will go bad before we use it all.