PT deck is getting splintery - best way to fix it?

The deck on our house is starting to throw a lot of splinters. It was built a year ago (last summer), and the contractor said to let it "age" until this summer before I stain/seal it. He said the PT lumber needed that long to fully dry so the finish would stick.
Well, I'm getting ready to seal it, and its got a lot of splinters on it. Most of them aren't a big deal, but the railings are pretty bad. I'm guessing that the constant rubbing from people going up and down the stairs has worn them a bit.
My question is, whats the best way to fix it? Should I just sand the railings (the only place that has actually given people splinters), or should I try to find some way to sand the whole thing (its 16x 20 or so)? If I sand it, should I worry about the sanding duest (its the greenish PT lumber).....

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