I agree that real chain has a place, but you might do well with the molded chain, too.
This might be another technique you haven't encountered yet - "drybrushing".
To do this, first paint the deck the final grey color it will be. Then get out some black paint and a small piece of cardboard or a 3x5" filecard. Get some black paint on your brush and then rub most of it off on the cardboard. Then, with your brush just barely wet, lightly rub it across the high spots of the chain. Practice makes perfect.
As far as real chain, model railroad supply stores usually carry small chain of 40 links per inch, or bigger at 36 links per inch. It is not the kind of studded link that is on the real ship, but in 1/700, it is the effect that is important. Also, those railroad chains can come in gold or black. My local shop carries the A-Line brand.
Practice. :-)
Good luck,
Rick