From the center of town in Gunnison: Drive north on SH135 to Almont. Turn right onto Forest Road 742 to Taylor Park Reservoir, all on pavement. At the intersection on the ESE corner of the reservoir, continue on FR765 to Tincup on graded dirt road suitable for all passenger cars. From Tincup, turn left (east) on FR267 and drive 4 miles to Mirror Lake. Passenger cars with better ground clearance may be able to drive to Mirror Lake. From the lake, continue driving south. The road will quickly become a 4WD type road as it drops down to the east shore of the lake and then heads up the valley. Drive to the coordinates provided and park off the road as best you can. This particular location grants an easy access down to the creek with minimal willows to contend with, however, once you cross the creek you'll have a short encounter with some man-eating willows before you break through to more easily navigated forest.
A second starting point is further up the valley by about three to four tenths of a mile. At these coordinates: N38° 43' 37.71"; W 106° 26' 08.61" you can park and hike SW down to the creek easily, cross it and hike up the other side with less competition from willows.
There is a designated campground with vault toilets at Mirror Lake. Before arriving at Mirror Lake, there are some at-large, primitive sites as you drive up from Tincup. There's also a trailhead parking lot with vault toilets just a short distance below Mirror Lake where you may be able to car camp for a night. There's also a primitive site at the south end of the lake.