rust on tub overflow when replacing drain pipes

I'm replacing the bath darin pipes for my tub which is an old enameled cast iron tub. The bottom drain seems pretty clean (just a little rust, not much) but the back of the overflow drain has some serious rust. I used a hand grinder to take a bunch of it off, and now I can see maybe 1/2 to 2/3 of the area as shiny metal. the rust pockets are even- there are little pockets of deep rust.
Question: I tend to be pretty anal retentive when I don't know better, and I'm inclined to take my dremel and carve out the rest of the rust even though that will take a while, and leave an uneven surface. Would it be better for me to stop where I'm at, spray just a little rustoleum on it, then attach my pipes? the kit comes with a gasket, and to be honest, I don't know how often the tub will even be filled anywhere near the overflow.
I'm just checking to see which is better- leave it level but pockets of rust, vs clean all the rust out, but have an uneven surface with pockets deep enough that the gasket probably wouldn't be certain to seal anyway.
Thanks, keith
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Auto stores have a variety of products that convert rust to a black compound that's paintable.

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Don't get too slap-happy with the Dremel, Keith. You're gonna grind yourself a pit and have a new issue. It sounds like all of the loose rust is gone. Now, I would spray it with one of the rust converting sprays (Loc-tite makes the one that I use most) and get the stuff solid and proceed with the job.

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Or just replace the pipe.

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