Liquid green stuff is perfect for boils, gore, and nurgle rot, and gap filling.
My Fiancé just pointed out that it looks like he is wearing a minion hat. Can't unsee it now.
These look incredible! Great basing, and fantastic colours.
For the conversion, get yourself a tyranid warrior or hive tyrant, but you should be able to get a cheap one off of anyone, they work perfect for...