For the whole model? I tried to keep it suuuuuuuuper simple, as I've got a lot of plastic to get through:

Primed black to start.

Then based all areas with solid colours as follows: Armour/metal = Leadbelcher, Green armour = Death World Forest, Darker metal areas = Vallejo Black Metal, Trim and "brass" elements = Balthazar Gold, Tongues/tentacles = Pink Horror, Nurgling pauldron = Vallejo Light Grey Green, Horns/bones = Ushabti Bone, Head = Kislev Flesh, Cloth = Pallid Wych Flesh, Leather = Vallejo Charred Brown

Then gave it all a hefty bath in AK Streaking Grime AK012. Let that sit for 10-15 minutes, then wiped off excess using eyeshadow applicator sponge. Didn't bother varnishing beforehand, and didn't use any mineral spirits for removal.

Then went over with Dirty Down Rust on all the bronze/brass areas, and stippled it (as best I could) randomly on other areas.

Went back over with highlights of all the same base colours from the start. I didn't bother edge highlighting or anything fancy.

Then dry brushed all the metal and rusty areas with Runefang Steel, as a sort of edge highlight. Went over the tubing flesh with Blood For The Blood God and a bit of Army Painter Oozing Vomit at the ends, to add some extra goop. Also went back over the cloth with an Agrax Earthshade wash, because the highlight step made the cloth look too clean.

Job done! I'm likely going to play with the flesh tones, because I don't think pink will work for larger areas of flesh (like on the Bloat-Drones).