This is the easiest route to ascend the Buttress.
From the Eagle Falls Trailhead, follow the trail for about a mile. The lake is a very nice picnic spot, although it can be crowded. Cross the lake outlet then follow a use trail that parallels the lakeshore. Towards the west, about 1/3 mile from the outlet and past the lake, two prominent gullies are visible leading to a ridge. Take the right gully and look for an intermittent use trail. Upon reaching the top of the gully, follow the ridgeline to the northwest for about one-half mile until reaching the Eagle Lake Buttress.
See this photo. Traverse up the class 3 slabs and blocks until reaching some class 3-4 slabs at a notch below the summit. You can rope up here, which is really overkill, or continue on to the summit block. A class 3 option is to climb around the north side ramp on the left side. The final moves on the summit block require straddling and slithering along the block and are exposed and unprotectable. The scrambling here is a lot of fun and the rock quality is excellent.
This route is commonly used for descending the rock climbing routes.
The class 4 sections are short. Climbing shoes are nice to have. If you want to rope up, a 50m rope will do the trick. 3 or 4 or cams, size 1 and under, are more than sufficient to get you up there.