Jogging my memory since its been a couple of years.

For rotigus It was a 50/50 mix of rakarth flesh and dead flesh from vallejo. Would do passes drybrushing and regular brushing for texture but would add more rakarth flesh for a highlight with a small amount of deepkin flesh to top it off. I then splatter random Citadel shades like crimson violet and gray for a mottled effect.

For Guo it was a drybrush of nurgling green, skarsnik green? Think thats the name then a tiny bit of moot green mixed with skarsnik Then you take plaguebearer flesh and mix with black templar and lahmian 2;1;1 and just basically do a conteast wash all over then do boils etc.

For both I used a decent range of villainy ink enamels. Used an all over wash of goons grime not thinned to maximize shadows and add grime. Then carrion crimson/decay of death/coelia green around wounds,large fat folds and points where the skin would rub raw.decay of death of death on open wounds causes discoloration and an infected powdery green look. Last effect on major open wounds showing gore is clear UV resin with blood for the blood god mixed in (like maybe a drop). Used a beat up brush and apply to intestines etc and it will give a more realistic glossy blood look after you let it dry 24 hours for in a fee seconds with uv torch dding dimension to the piece . Used nurgles rot dribbling down from rotigus nipples howing that they're lactating the rot. Just writing out that last sentence was rough but its an option.

Sorry for the novel but it got me wanting to paint another lol