I think he also works directly on the computer. I've recently seen one of his drawings put next to the reference photo and the colors were really close and the poses too, so I think he does work directly digitally as well.
Probably the only essential things you would need are: experience/practice, a wacom tablet (or another drawing tablet in general), patience and a good drawing program, like photoshop or SAI.
And don't be afraid to use references, if you're just beginning
