How do I soften up gumpaste that is very stiff, not dried out, just very tight and not elastic?
(hope that makes sense)

I take a little shortening and work it in pulling and stretching it. It softens up pretty well that way. The heat from your hands helps too.

Yup, a little shortening. Have you tried Nick Lodge's gumpaste. It looks like concrete as your mixing it, but once you knead it, so nice and smooth and good stretch.

If you made if from scratch, try using a little less tylose next time you make it. I have a recipe that yielded incredibly stiff gumpaste that dried too quickly (the recipe that comes with the cake cricuit) so the next time I made it, I decreased the amount of tylose by 1/3 and it works perfectly.

Shortening works great for stiff store bought or other recipes that I have tried but didn't work so hot on the super stiff GP

HTH!!!