what exactly should i use to lube it and how?

Well, I don't know what you should use, but you can see in my photo I squirted the wire with motor oil, and allowed it to run down into the cable.

However, the cable is a direct path to the transmission, so someone will say I am potentially contaminating its fill of Dexron. I don't guess I used more than 2ml of oil. Just enough to get oil around the wire inside the cable.

If you can't get the wire to retract, or push it in (gently) it might take a long time hanging the cable up high and allowing the oil to migrate to the rust. Good luck. The cable on the '89 in my picture wasn't so much stuck, but maybe a bit sticky.

In the photos below, I am lubing the hood release cable. Maybe this technique, using a grommet and some vinyl tubing might apply to the kickdown cable. Then perhaps you could fill it with ATF?




--
Art Benstein near Baltimore

Never miss a good chance to shut up.