This is basically the easiest way up Montgomery any way you shake it. The start can be made at any Boundary Peak trailhead, as the route traverses Boundary's summit. Also see supplementary details on the main Montgomery page.
Once the summit of Boundary Peak is attained, Montgomery and the entire traverse is in full view to the southwest. Proceed down the SW ridge a 1/4 mile to the saddle, staying to the west (right) side to avoid too much difficulty. Pass the large outcrops of gendarmes at the point where they meet the talus, and the scramble will be kept to a loose class 2.
Once at the saddle (where, incidentally, the NV-CA state boundary crosses), begin the 1/3 mile climb to Montgomery's summit. The route is fairly steep and loose in places, no matter which side is taken. In some places, it is easier to stay on the crest of the ridge --- pick your poison. Approach the final slope to the peak on the east (left) side, scrambling up a short, steep section to the top, taking care when reaching the crest to avoid a long vertical drop on the west side...
No rock climbing gear is required for this climb. The final slope to Montgomery is fairly steep and tends to harbor snow longer than Boundary. Crampons and/or ice axe may be desirable if going during consolidated/frozen conditions.