Metalic buttons, I use metallic paint and then depending on the color of uniform a drop of wash to let capilary action surround the button and define it a bit more.
For subdued buttons, whatever the appropriate color of the button and then a wash, once again so that the button is defined with a darker color. A little drybrushing to highlight the area dependent on light direction.
I use a 10/0 liner a 3/0 and a fine round for much of my painting.
Mike
"Imagination is the dye that colors our lives"
Marcus Aurellius
A good friend will come and bail you out of jail...but, a true friend will be sitting next to you saying, "Damn...that was fun!"