More open and sunnier than either Raptor Canyon or Water Canyon, the headwaters of Brush Canyon are similarly pristine and peaceful.
Begin this hike, by heading south from the equestrian campground in Aliso Canyon. When you reach the road that leads into Water Canyon, turn right (west), then immediately left on a road that winds up the hillside to the south. Bear right at the next fork and continue uphill for 0.5 mile. Brush Canyon now lies below and to your left. Where the road levels out, find the seldom used path that slants left (southwest) down into the big grassy bowl to your left--Brush Canyon's head. After about 0.3 mile you reach the first of several deep, wooded ravines that sweep down from the lip of the bowl and join together to form a single V-shaped canyon. Exposed on the hillsides in this area are some small outcrops of sandstone, part of the marine sedimentary formation that underlies this area.
Next, pick up and follow the obscure remnants of an old road on the right (south) side of the first deep ravine. This leads down through shady thickets of live oak, walnut, sycamore, and toyon--good places to rest or have lunch.
When you reach an old cattle trough, once fed by a now-defunct spring, cross a steep tributary ravine on the right and continue (staying south of the main ravine) across a grassy slope dotted with sage bushes. After some mild brush bashing west (watch for poison oak) you reach a dirt service road adjacent to the buried Lower Feeder aqueduct, which supplies Colorado River water to Orange County. Continue east on this road, up the hill overlooking Brush Canyon and back over into Aliso Canyon.