I have used WD-40 to "revive" an old dried-out ribbon. It seems to both soften the dried ink and lubricate the print pins. But it doesn't add any ink, so eventually you need to re-ink.
I have owned two "MacInkers", devices designed for re-inking ribbons, but I got rid of both due to what I consider design flaws. First, the ribbon and ink dispenser are oriented horizontally, which means the bottom part of the ribbon tends to get more ink than the top; there are two holes and if the ink level drops only one hole dispenses. Second, the drive motor is small, one-speed and one-directional. Third, the drive adapters rely on a clumsy set of "claws" to hold the ribbon cartridge in place and lastly the ribbon path has to be adjusted according to the cart being serviced. I built my own in answer to these problems**. It uses a 1/2-inch variable speed reversible drill as its motor. The ink dispenses from tiny holes in the bottom of a tube (1/2-inch PVC). The ribbon threads over two roller-skate wheels which hold the ribbon against the ink dispenser. Two garden-hose washers keep the ribbon in line. The final hurdle is the ink consistency: Too thin and you have blotchy pages; too thick and it doesn't distribute evenly on the ribbon. I'm afraid you have to experiment there. I can only say that proprietary formulas sometimes include alcohol, glycerine and/or ethylene glycol as well as lampblack carbon in an oil base. -CH- ** https://drive.google.com/file/d/1NDMLCdHa01qJSXpLCQnhWjWctH4XQ7lf/view?usp=sharing
