There is a glaring ommission in the approach options - the Ptarmagin Traverse - which begins at Cascade River Road. (The recommended Bachelor/Downey Creek approach is a long, unappealing brush bash. By doing Dome as part of the Ptarmagin Traverse, you limit your brush bashing to one unpleasant day AND you get the pleasure of having done a classic, beautiful high alpine traverse.)
From White Rock Lakes, ascend the ridge to the west. Traverse south until you reach the Dana Glacier. Follow the Dana under the cleaver and up to Dome Glacier.
I plead guilty to assuming that you would read the Overview section. Please read the second paragraph where I attempt to depict the difficulty of the Downey/Bachelor approach, and the third paragraph which points out the PT approach without going into a lengthy description of the route. Several of us have discussed putting up a PT page here at SP, but it hasn't happened yet.