Well you're off to a good beginning with the references, must-have starting point for something like this.
Two main things I can suggest, the first is paint consistency: thin the paint just enough to ensure good flow (depending on what you're using this might be straight from the bottle, but you're likely to need to dilute just a little bit). This will give the ideal balance between easy brushing and opacity/coverage. Second thing is to practice painting the pattern off the model, on a scrap of plastic card or something like that primed just the same as the model will be; only commit to the bust once you're comfortable painting the pattern consistently and evenly.
If you find it hard to get right after a few tries you might try painting a test at a larger scale - possibly even half size - and then reducing down in stages to 1/10, that can help in other contexts and it might work here.
Einion