I know you said it wasn't what you like, but hear us out. This is how I do my Nurgle Tentacley bits (and other bits like wing membranes).
Start with a base of vallejo royal purple. Then drybrush evil sunz scarlet then finish with a drybrush of vallejo iraqi sand (aka ushabti bone). Wash the whole thing (I wash the entire model with this at this stage after blocking in colours) with vallejo smokey ink watered down to your liking then finish with watered down Nurgle's rot.
It gives you something like
this. Though keep in mind the flash was on when I took those pics so the effect is a bit more subtle
IRL.