First of all, Welcome to the site! Good to see another OKIE on the site .
Is the zink flaking off, or do you want to color match all your hardware?
If your car is going to be a daily driver you could just get a can of chemclean and dip them in that over night, cheap parts washer.
Anything more than that would be overkill unless you are wanting to build a show car. You are right, it would add up in a hurry if you did all your nuts and bolts. You may just go with some of the most visible ones. Not sure of all the options for steel nuts as far as coating, possibly annodizing?
Good luck.