the way is to implement the buttons using facets.
Each RF component comes with set of predefined rich-* CSS class set for key elements of HTML markup. You can check user guide for a list of such classes.
The facets way seems ok for me. I haven't seen the "disabled" facets during my first reading. Sorry...
According to nbelaevski, there is a predifined rich-* CSS class. I haven't found it for disabled buttons images in the ordering list component.