This route description is based on a sequence of a loop hike that begins at the Pieplant Mill site, climbs up Jenkins Mountain, then continues to UN13,140B. From UN13,140B, it's an additional 1.5 rugged miles to Grizzly with 900 feet of gain. To complete the loop, you'll hike another 3.2 miles back to the mill site with an extra 260 feet of gain.
From UN13,140B, follow the ridgeline SE a quarter mile or so on fairly easy terrain. As you progress, staying on the ridge crest will become progressively more difficult. Shortly, you will come to a section where you will either have to do some serious climbing/scrambling or abandon the ridge and head down into a large, steep, loose, rock-filled couloir to the south. Drop 400 feet in elevation down that couloir and then start looking for an exit. The descent goes quickly on a lot of scree. Head east over a more level area to a minor basin at 12,600 ft. This will mostly be covered in boulders. Ascend to the saddle between Pt. 12,882 and Grizzly on more boulder rubble. Follow the ridge SW to the Grizzly summit on yet more rubble. With some luck or if earlier in the season, there may be snow fields in the minor basin that will negate having to clamber over the relentless boulders to reach the saddle. Once on the ridge however, you will have no other choice than to navigate the innumerable rocks and boulders to the summit. It will take about one hour or more to traverse from Jenkins to UN13,140B, then at a minimum, another hour to reach Grizzly.
To descend and finish your loop hike day, head SE off the Grizzly summit and down a rocky, rounded ridge. If early enough in the season, a narrow band of snow may allow a glissading descent along a portion of this ridge. At 11,400 you'll reach some trees and be able to leave most of the rocks and talus behind, but not before one final trek across one other boulder field. Continue SW descending through easy forest until you intersect a trail known by several names depending on the map used. The USGS quad calls this the "Rocky Mountain Pack Trail." The most recent Gunnison National Forest map identifies this as Trail #414, aka: the "Timberline Trail." This trail follows the wilderness boundary and heads generally NW and takes you all the way back to the Pieplant Mill site, for an easier and more pleasant finish to your day. This descent will add 3.2 more miles to the day for a total loop of 9 or more miles with total elevation gain of over 4,800 ft.
Links to other information, routes & trip reports for this peak that may be helpful.