severely rusty diff covers?

I am swapping my stock diff covers for RuffStuff ones. My problem is that the RS covers got left outside in the rain after I painted them (if you have significant others you shouldn't need to ask about why something like this might happen), and now have gobs of rust all over the inside & mounting rim. :banghead:

I started to hit them with a wire brush on my drill but then I stopped, 'cos I remembered everyone talking about how you weren't supposed to gouge the rim. Now I'm trying steel wool but that is taking forever and doesn't seem to want to get in around the weld bead.

I searched around but couldn't find anybody who mentions this kind of situation specifically. Will brake cleaner take off rust of this level? Will wire brushes really gouge them that much? I also have LubeLockers for them (I hate scraping RTV), but will that mean I'm more likely to have leaking if they aren't perfectly flat? If I miss a tiny bit of rust in the weld bead areas am I just asking for my gears to be sanded to shreds?

The wire brush will be fine. Won't hurt a thing. You can use sand paper or bead/sand blast as well. Clean with brake cleaner and then install.

You could try naval jelly (a gelled acid made for rust removal) but sand blasting would be best if you have that option. A wire brush and a whole bunch of elbow grease will work in a pinch.

I'd just use a brass wire wheel in a drill. Brass is softer than steel, so it'll strip away the rust without damaging the remaining steel surface.

I keep one around for this very purpose. It would be great if I could ever find it when I need it.