Yup I did all that with the hair and beard repainting. Seriously loving it now. People have been asking me I know so I’ll post pics eventually.
As for the colors I always use Tamiya acrylic and com arts translucent secondary colors.
I never really keep track of how I mix colors, I warm it up or cool it down based on my classical training in the fine arts, just wanted to go with a warm gray with lighter highlights in certain areas. Used the com arts ocre color for his beard as that’s the most yellow area on his face. Lighter highlights at the corners of his goatee and bottom of the beard.
Did not strip any paint except his hairline it was too abrupt and I wanted more subtly as his hair is thinning at the top.
Never use reference pics from the show for stuff like that unless the character is wearing a wig or something like that. If it’s their natural hair or face tone use PR or red carpet shots always. It’s the most honest. Artistic lighting from film production influences how things look on screen.