Norcal,
Once you move towards NAP, everything will come into focus. As you move toward the NAP area, you will see the trail that descends, which will eventual take you to the upper part of Rock Creek, two junctions you will go through are very well signed. Just check you map and this will all make sense.
Given my druthers, I would use Army Pass to approach Whitney from the west, NAP is second and Cottonwood last. I love Army Pass because its direct it's 300' lower than NAP. NAP is my second choice because I can cut a mile off the distance by using the South Fork drainage and going x-country through the South Fork Lakes and, finally, my least favorite is Cottonwood Pass because the trail is like a roller coaster, extremely sandy and there is very little protection from the sun, until you drop off of Siberian Outpost.
