I used a silicone automotive adhesive from Advanced Auto. I put it on with my finger and then wipe off the sides of thecrack with paper towels. The silicone will dry and become less shinny with exposure. This is not a perfect repair but not too bad either. The silicon I used is black which matches my dash so that helps. My crack was approximately one inch and relatively small. I am really picky so use that as a reference.

I use 303 Protectant very regularly to prevent further cracking. It has been a year and no further spreading. Still looks the same as the day I repaired it.

If really bad in appearance, you can always go with a dash cap.