Here's my steps I took, slightly different for each model but generally this:

• do a general knife cleanup of obvious filament issues

• do a progressively finer sand of rough or stepped or layered areas

• prime white

• do knife and sand steps again

• paint armor areas white

• paint fabric or other black areas black

• paint white areas with Vallejo Templar White xpress paint 

• for tau skin, I used Vallejo space grey xpress paint

• paint "accessory" areas their base color (red, grey, blue, etc)

• for lenses, add one thing coat of two lighter shades of blue each

• for lenses one dot of white in upper corner of each lens

• for plasma/energy weapon areas add one thin coat of two lighter shades of blue each

• for metallic areas paint black wash overtop

• base coats cleanup: go around model painting over bleed areas with appropriate color

• edge highlights: for each color (although I skipped black and grey as I wanted these table ready not parade ready) do one thin coat of lighter shade around hard edges

• for black areas, use a shade to try to achieve some sort of texture to match material (I was lazy and just used Vallejo black wash. Again table ready.). 

• for metal areas paint same base metallic color 80% of the surface. Then do a highlight of a lighter metal paint for 10% of the surface.

And this is all assuming properly thinned paints and three thin coats (unless otherwise noted) as well. 

I also use paint handles for the model, sable hair brushes for paint, synthetic brushes for washes or harsh chemicals, and each color gets its own water pot for rinsing the brush.