I've tried using
GW green washes in the
GW water affects and i found it went a bit cloudy and had to do a few more layers to get the shine back but didnt look right, not sure if i had a dodgy batch of it tho! , always worth a go on a tester
In the end for that toxic kinda look, i based the area i wanted it on in modeling sand for texture, then just mixed a mix of different green paint into pva glue, whacked it over the sand in quite thick layer as it goes down when it dries, then added water effects, came out ok,
Hope thats of some help
T-M