I painted my first crater. Here's what I did:
brush all the raised surfaces with codex grey, leaving the raw dark plastic in the recesses.
Wash the whole thing in devlin mud
wash bits of middle in chaos black and some recessed bits of crater rim
drybrush exterior and around rim with codex grey
drybrush interior and around rim with scorched brown
drybrush the interior with chaos black, and some recessed bits of crater rim
drybrush around rim with kommando khaki