I have not tried this technique, but I heard if you brush Elmers glue on before you paint something it will result in cracked paint, but all the videos on YouTube are done on wood. You may want to practice on metal that already has a base coat to see if the technique would work for you.
There are lots of neat videos on YouTube describing a few different techniques. I searched “cracked paint elmers”
Last edited by Speedracer; Fri Apr 30 2021 08:41 AM.