I've been trying to practice restoring this part of strap from the junk drawer however I can't figure out how to brush the steel while leaving the decorative screws polished (the screws are nor removable).

I can't mask the screws off with tape because they are to small to cut a regular shape. I tried to mask them with Lacomit but the brushing process removed the Lacomit and brushed the screws. How should I do this. Is there a hard varnish I can coat the screws with, brush them then dissolve the varnish somehow?
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