These two-toned gel pen beauties pictured here I've had for 20+ YEARS. Do they write? Ha, no. Let's not kid ourselves. BUT the ink in the barrels is still good. For these, I took the metal nib off the top to expose the top of the plastic barrel and with a very tiny paint brush I was able to paint this part of a seashell with the ink. It was a little bit of work but why waste pigment?
I only had one pen that didn't cooperate as well with a paint brush because the ink was so thick but I was able to scrape out the ink (or you could keep cutting the ends off with scissors) and onto a page for a two-tone background.
Since the ink in gel pens is a solvent based ink, I would recommend cleaning your brush thoroughly after use other it will get very, very sticky.