Ron in Sterling, CT
I agree with Jack on using a razor blade scraper to remove the crusty rust. Be careful not to press to hard and scratch the saw plate. I would start with a 320, or maybe even a 440 grit paper, with WD-40. 220 grit will sometimes scratch the saw plate.
On the bit brace I would clean it up with some 0 or 00 steel wool, apply some light oil and put it to use.
My 2 cents. Good Luck