All the Plaguebearers have a lot of pustules, and some of them are bursted open. To get the dripping phlegm I used Vallejo Model Color Foundation White and (once the white was dry) GW Technical Color Nurgle's Rot.
My goal with the Plaguebearers was to get a unit table-ready as fast as possible without loosing myself with details (and waisting time). By adding all those additional effects I am not sure if I haven't overdone it. For one thing because now all the other Nurgle miniatures need the same details for consistency and for another thing the miniatures got more colorful than planned.