Birkenfeld Mountain is a summit that can be done as part of a challenging three peak traverse that would include Three Corner Rock-W7W/LC-101 and Greenleaf Peak-W7W/LC-104. Or Three Corner and Birkenfeld and back the way you came - those two summits make for a 10 mile day. The full traverse is about 12 miles and you'd need to drop off a vehicle or have two parties traveling in each direction to make a go of this.
The Pacific Crest Trail goes near the summit of Birkenfeld, but you'll need to travel cross-country through the woods a short distance up a steep slope to reach the activation zone - try leaving the PCT around 45.7141° -122.007°. We found a spot that was fairly open to set up near the summit. There are no views but plenty of trees. See this report on SummitPost for more information: http://www.summitpost.org/birkenfeld-mountain/417200