On Colorado State Highway 69, just south of the small community of Hillside, turn SSW onto CR198 which shortly turns and heads due west for 2.9 miles to an intersection with FR337. If you find yourself at the Rainbow Trail Camp, you've gone too far on CR198. The intersection should have a Forest Service sign for the South Brush Creek trail. Apparently the San Isabel National Forest does not refer to this trailhead as the Ducket Creek TH, but that's how it is designated on the Trails Illustrated Map #138 for the Sangre de Cristo range. FR337 will head south & west and in just over a mile will intersect the Rainbow Trail. This is where you should park. To get to both the North and South Brush Creek trails, you'll need to head south on the Rainbow Trail. It's approximately 5 miles to the S. Brush Creek Trail on the Rainbow Trail. The link below is to the San Isabel NF description of the Ducket/South Brush Creek TH.
We have never utilized this trailhead so the following information has not been verified, but it appears from Google Earth that shortly before reaching the trailhead, there appear to be numerous primitive campsites you can pull off into. The Forest Service does warn however, that you'll be driving through private property, so be careful.