I'm in the process of stripping paint and sanding off surface rust from my Univega Gran Turismo frame.

How does one protect threads and canti posts? What about the bearing race on the fork crown? Will my front derailleur still clamp on?

fd should be fine. The guy I've had do powder coat knows to protect threads. I ended up sanding off the canti posts. You might ask if the powder coater can mask them, it's a pain to get off.

I generally expect to face and chase everything after a paint job or powder coat. I'd rather do that than have those parts masked.

I have a friend with a powder coating business and I've helped him during busy times. Tell your coater what dimensions need to be protected and he should be able to take the necessary precautions. We had a bucket of different size high-temp silicone plugs we'd use to protect bearing races and internal threads.

So true, masking/plugging leaves fillets of paint in awkward places.