I may have a tip or two for the white parts, since i am in the middle of painting 2.500 Points of Tau in a nearly complete white scheme. Last finished miniature was a Riptide, you may take a look at my gallery for reference. :>
The problem with white is, and this is the part nearly everyone has a problem with, (even the guy at
GW i asked about how to paint a clean white armor....he said "dont"....
lol) you see brush strokes or it lookes like toothpaste. Well, do not paint white directly.
Try painting the white areas with a very light grey. I myself use
GW Ulthuan Grey. You then highlight all borders and edges with pure white, i use Ceramite White for that. And that magically turns the whole area white for your eye! A very clean looking one too.
All you have to do is dillute the paint well. Not so much that it could be a shade, but it has to be flat on your pallette or whatever you might have. Ulthuan Grey needs about 2 layers, max 3, always wait until it is compeltely dry. If the surface is lightly wet you scratch the paint, resulting in even more brush strokes.
I actually prime my Tau
black, give the white areas a Celestra Grey base coat, ink it heavily with Agrax Earthshade (gives a warm tone to the white and since i am leaving very deep shadows in all recesses the minis get a slight "comic" look, which fits dem mechs good), and follow up with the Celestra Grey as described above. It is a lot of work really and i kinda hate myself for choosing this scheme. But looking at my finished minis, i think its totally worth it.
If you are just lazy, well i cannot help with that
Greetings =)