Tiny metal specks have covered deck in rust. Help!

[faith]

The dear skipper in an effort to make the teack trim on our Pearson 36 look great used fine steel wool to "sand down" that last coat of varnish. Then he carefully blew all dust off with a hose. Or so he thought. We came onboard to find large areas of tiny rust spots everywhere on the deck. We tried Zud and a scrunge and that seemed to to the trick. For a few days. We've repeated the process four times and still more rust comes back - different spots each time. Any suggestions? (We're planning on getting a Freedom 35 for the next boat. One reason - NO TEAK!) We are trying to keep our dear boat pristine since she is now for sale. Thank you. Faith