Andy,the way i put in the five,o' clock shadow is to do it when the paint is still wet add a touch of grey in a line down the jawline and stipple it in,don't try and draw the brush up or down,but dab it,as for the sheen,i paint in oils,and sometimes,depending on the colour it comes out with a sheen,to be quite honest it is something i don't bother about,if you are happy with the result,as you should be,just take pleasure in the hobby.
Arthur