Denny just recently posted his tutorial on 'edging' your models with markers.
An better alternative is to pick up a set of watercolor paints, a small set that includes at least yellow, red, brown, green, and black would be ideal. By using a slightly watered down color (less pigment, more water) your edges will generally match the printed detail better than markers can, and the paint will wick up into the seams between pieces better than a marker can, giving you better coverage, with less work. Just be cautious about the amount of paint your using, lightly painting the model and allowing it to dry, then going over it again is far better than a single coat that may warp the paper/card.

Set the ink from your inkjet printer using a LIGHT spray of clear matte acrylic, your ink will be far less likely to 'bleed' if you get heavy handed with your adhesive, or with the watercolor from the tip above.

Rather than score the cardstock, try using a smooth tracing wheel (available from sewing centers, or Wal-Mart) on the reverse side of the card. This will crush the fibers of the card allowing it to fold in that direction easily, and keeping the printed detail on the front of the stock FAR more intact than scoring.

Or a ball point pen w/o ink to score. I forgot this trick..






Ironkingdoms cool....