You could try the simple prime white then paint with washes trick.
relativly easy quick and easy for nurgle. and daemon type things
"After giving the model an undercoat of white and letting it dry I applied a wash of Game Ink Sepia all over the model. Once this was dry I did the same with Game Ink Black Green"
Id also pick out some areas with purple, reds blues and blacks in areas and shade bruised wounds and entrails type areas
though for red
id personally use secret weapons ruby wash
so personally the way i would do it (as i plan on doing some slannesh stuff in a similar manner) by first priming white, touch up areas with a similar white to make sure you have full coverage, as the blog did
id do sepia ink on all the things, then
id ruby wash on entrails and pimple area, then purple around it
then green avoiding the more red features but blending it in a little with layers.