I tried the baking soda+super glue trick, and various versions of it using little pieces of cut plastic, different paints, gorilla glue, epoxy. On two different S14 dashes.
So far nothing worked 'perfectly' (cracks re-appeared but much fewer/smaller) but as with most things, the less I care about it when doing it the better it started coming out.
Next time I am going to try some higher quality 'glue' (probably JB KWIK or similar) I've had good luck with that stuff on motorcycle body panels, sanding and painted over JBkwik, are still quite flexible and don't seem to crack. Couple months I'll be doing that.
I'm not concerned about texture. Just low cost and no cracks. So my method is basically, sand/rough it, clean it, fill it, sand it smooth, hit it with random black paint. Done.
You can see how bad it was cracked, pretty ruined junk.
It looks 9999% better but still has myriad tiny slivers of cracks since then I need to go back and fill (like I said I'll try something new)