Rust never sleeps on a steel boat, part 2

We launch Alchemy May 7, and there's some stuff yet to do to the hull. Some "rust bubbles" have appeared where the barrier coat seems to have failed. While I intend to have the entire hull laid bare and fresh primer and barrier coat put on before we go, there's no reason not to fix these particular spots now with a grinder, a "flapper disk" sanding wheel, and some rust-binding primer.

We will be using this stuff on the recommendation of the previous owner and others:
http://www.petitprod.com/catalog_browse.asp?ictNbr=95 (you can download the PDF if interested). Three tacky coats of that later, we'll apply Pettit Premium ablative anti-foul...it's only good for a season but suits Lake Ontario until we redo the bottom entirely and switch to a "hard" antifouling for tropical waters.

I'm actually looking forward to this job as it's been difficult to do much on the boat over the winter due to the distance (by bicycle at least) to the storage yard, my work load, and the fact that the weather has been fine when I've been working and awful when I've been free.