Dash cracking prevention

I know UV protection is the way to prevent cracking (garage, cover, sunshield, ...). My '79 280zx has a single small crack right in the middle. I actually bought a Covercraft soft cover to install. Before I install it, I was hoping to give it a good conditioning and rejuvenate it if at all possible. Google and site searches aren't turning up anything concrete.
What do you guys use to keep it conditioned and prevent cracking?