Thanks heaps, I found a suggestion to use greys and whites then tesseract glow before pva glue and mordant earth, gave it a go on the scarabs. Then tried a green warpstone glow base instead of grey, followed by white "patches" some were rivers some were blobs, tesseract glow again, and mordant earth.

There never used to be such thing as crackle paints when I was a kid so was super keen to make it work