The trail up Echo Canyon begins by heading uphill to the north. After about a quarter mile, it comes to a creek crossing. 4WD could be driven to here if you have one, but there's little point in doing so. The rough road will not gain you much time. The road ends at an old building's concrete foundation, about 10,200 ft. The trail starts at a creek crossing which is east of and about 25 vertical feet below the foundation. At one point, there was a sign post here indicating that this is the start of the Echo Canyon trail, but a recent report indicated that sign is missing. A June crossing of the creek can be problematic and will likely require wading. A 2016 trip report from a reliable source says they found a log to cross on about 100 feet upstream. Do not follow the USGS map at this point which would have you believe that the trail stays on the west side of the creek and crosses to the east later. Once you cross the creek, the trail follows on the east side of the stream and remains there.
Continue on trail upstream and farther up, it will rejoin the old roadbed that goes to the mines. At 11,130 feet, there's the junction where you should continue on the old mining road which will begin switchbacking up the hillside to the right. Continuing to follow the trail along Echo Creek will take you to a basin south of Casco Peak. Approximate coordinates for this junction are: N 39° 04' 58.73" W 106° 28' 12.62". Usually this turnoff is cairn-marked. Head up the old roadbed which will switchback numerous times. The Last Chance Mine will come in about 1.25 mile. The Golden Fleece Mine will come in about another mile at about 12,700 ft. Continue Class 2 hiking up a steeper, rocky slope to gain the south ridge of Bull Hill. Once on the ridge, it's easy walking on grassy tundra with embedded rock to the summit. As you hike up, an impressive vista of the surrounding mountains will unfold.
The summit, as mentioned before, offers an impressive view of Mt. Elbert to the NE and La Plata Peak to the SSW. You will likely see hikers on Elbert if it is a weekend, but there's a good chance you will have Bull Hill all to yourself. This is the highest "hill" in Colorado. Descend as you came and if you find the switchbacks on the old road to be tedious, there are places where you can expedite your descent on some scree slopes. With our later elementary-age children, we completed this hike in a very leisurely seven hours.
Alternate Route: Another route for Bull Hill was promoted by G&M in their book. The route utilizes the Black Cloud Creek Trail which is used by many for a southern approach to Mt. Elbert. The trailhead is .7 mile west on SH 82 of the Twin Peaks Campground entrance at these coordinates: N 39° 04' 08.18" W 106° 26' 01.42". Parking is just off the highway. Follow the trail up Black Cloud Creek to a trail junction at 11,000 ft. Take the left fork and hike up to the vicinity of the Fidelity Mine. Gain the SE ridge and continue to the summit of Bull Hill on mostly grassy tundra.
Alternate Route #2: Bull Hill can also be climbed from Casco Peak via the connecting, two-mile long ridge. Eddie Mack reported doing this traverse and rated it a Class 2 with no serious difficulties. It took his party about 2.5 hours to make the traverse. For the most part, stay on the south side of the ridge crest. They reported finding faint trail. From the summit of Bull Hill, you can "ski" on scree slopes back down into the South Halfmoon basin if that is your desired return route.
Links to other information, routes & trip reports for this peak that may be helpful.