you will need:
a stanley knife
super glue
a glue gun lowtemp or green stuff
pin drill
graveyard earth and vomit brown paint
imperial guard model
chaos possessed or spawn sprue
the colours of any imperial regiment
step one:
get the model using the pin drill dril small bullet holes in the armour
step two:
using the stanley knife slice some of the limbs preferably not the legs use the glue gun on the cut and let it drip down the model cut holeds along the spine and place chaos accesorie things (i.e tentacles) glue them in with the super glue p.s try to make the model a zombie like as possible not a weird conglomeration of spines and tentacles
step three:
once your happy with the model undercoat it paint/spray then paint the model's flesh parts vomit brown before it dries paint on some graveyard earth in small amounts DON'T let it swirl one finished drybrush some more earth on the finally highlight with tiny amounts of bone for a ghostly look highlight with codex grey instead