Once the Aztecing is finished, mix up a little Black and Wolf Grey in a 1:2 ratio, and with a Size 00 brush, tidy up the grey areas. At this point, I picked out all the surface greeblies which were not to be yellow in colour.
This is the stage where getting your lines straightened out is crucial, as afterward there will be a lot more Aztec detail all over the place and trying to correct the lines then will be a nightmare.