When the wheel covers are painted by professionals, the masking of same does not seem to be an issue at all. I had 8 wheel covers painted (4 of mine and 4 of Tom Rose) some years ago locally, and a "replacement" 2 years ago. They were different shops, neither batted an eyelash. I mentioned the mask and the second place knew about it and said no, he'd prefer to mask himself. It was a non-issue.
Prep, masking and painting ran about $40-50 a wheel cover.
If you are doing it yourself that's another story.