Use the excellent topo from www.tabvar.org/ (see the downloads section) and you can't go wrong. All (most?) belays are fixed with bolts. Take the right finish (pitch 12/13) as this is probably the best pitch on the route.
The gear is there when you need it, but as is typical with Rockies limestone you should expect to have to run it out from time to time.
The route is obvious, but the approach is not.
First you must reach the hut. From Castle Junction go west on Highway 1A for a few km to reach the trailhead for the Castle Mountain fire lookout. Follow the trail to the lookout (1-2 hours) and then pick up a smaller trail that crosses the gully (east) before heading steeply uphill to the headwall.
Look for a diagonal break in the headwall (small cairn). Some steep scrambling for 30 feet or so leads to an easier climbers trail. If you are doing anything hard you are off route. Follow the trail to the hut (about 3 hrs from the trailhead). Brewer Buttress is visible from the hut as the last buttress before the Eisenhower Tower.
From the hut on Goat Plateau, follow the trail east along the base of the cliff until you reach a bay on the right side of the buttress. A belay bolt marks the start of the route.
To get down, walk WAY west to reach a large low angle scree gully. Two or three short rappels are required near the bottom of the gully to bypass chockstones.
A small rack of nuts and cams is sufficient. Bring long draws. When we climbed it we had double ropes, and I would recommend this to avoid rope drag and to facilitate retreat in the event of a storm or accident.
Glenn T. in front of the Castle Mountain hut.
A topo of the route. A larger version is available...
The first pitch of the route (this was by far the ...
Pitch 9, the crux of the route at 5.7
Pitch 2 (5.5)
The correct descent gully.
Pitches 3 and 4, seen here, are usually combined. ...
Although only rated 5.6, the route is very steep w...
Pitch 5 (5.5)
The right finish (recommended) takes this steep wa...
The view of Rockbound Lake from the summit.
Brewer Buttress climbs the corner to the left of E...
A huge chockstone near the bottom of the descent g...
Looking up the steep 5.6 corner of pitch 7. Nice p...