Goey is rot & indicates it needs to be discarded. Goey is too far gone to be salvaged. Nice that you wish to try, but these are not hardy plants & I suspect it's a lost cause.

If you're determined to try, pls, scrape the bare branches w/ your fingernail & look for green tissue (still living). If you find any, that's worth TRYING to save.

If no green tissue is found, I wouldn't bother, I doubt these plants would survive temps in the 40s, much less a freeze. So sorry.

I wonder if hoyas can regrow from the roots if those are alive, even if all the stems are dead. I do not know.

But sounds like it was days or longer in freezing weather. If so, then the plants are now spending their days "happy"... "upstate"... "on a farm". (Sorry.)

Yes, it sounds like it got cold enough the roots surely froze solid, too. Not much chance of recovery. Hoyas can handle a few hours around freezing, maybe even a bit under if protected. I've had Hoyas on my front porch when it dipped to freezing overnight with no damage whatsoever, but that's for just a few short hours and nowhere near zero. I think you might as well toss them.

Denise in Omaha