as said before, here an example of how I would paint dirty white (figure is not ready, just a control picture to see the bad areas better - the makro is too honest...)

Painting was relatively easy - started with very light grey, painted white lights on all surfaces that are directly lighted and used light brown-grey washes for the shadow areas - "Worn Patina 1" from the range of "True Earth".
That't all...
David - as you said:patience is key when you are figure painting - and using a good brush and a 2.00 dioptres reading glasses

Brushes from Windsor&Newton or Raphael are very good for acrylic paints, durable and with a good point, very recommended by many figure painters. Don't use synthetic brushes for acrylics - that will not work.
... and last but not least the male comrade for my little zombie schoolgirl:

Both figures from the range of Not Yet Dead Miniatures (NYD-Miniatures) and 1:35 scale.
Cheers
Thomas