Upper Approach:
From Wishon Reservoir, go across the dam following the pavement to the gate just before road's end. This left turn takes you to the dirt lot for the Rancheria Creek Trailhead. Go past this TH, veer right at the first fork, staying on the main dirt road (low clearance ok as of Autumn 2014). Follow it to a large dirt pull out before the locked gate. Hike the road from there to the first big left hand bend. At the bend go straight thru a small clearing with new growth trees instead of the road. From near the end of the clearing, veer up and left on bulldozer cuts with dirt berms then open forest until you rejoin the road (or just follow the road around the switchback).
Continue on the road for a about a half mile. After a seasonally lush/green area, and before the road starts to gently go downhill, look for a clearing with new growth next to the road. A yellow trail tape marks this faint hunter use exit point. Veer left into this clearing and enter a meadow area. Cross the meadow heading SE to gain the ridge in the distance. Don't go up the steep section of the ridge, elevation gain to the ridge should only be 50-60 feet or so. From that ridge contour left through some old growth timber stumps that has been cut and burned over the years. This goes a little uphill.
If done right you'll go up in elevation to a point on the ridge with a point of rocks and a meadow area below it on the South slope. Cross below the point of rocks at the top of the meadow/fern area. Contour around the slope heading for more open fern and grass slopes. Just beyond this open area of the ridge you'll start to see more boulders and something of a rock-band. Aim for the notch between two prominent rocks. Some short brush crashing as you go up between the rocks may be needed. If you approach and get to the break in the rock band you should now see the West side of Hoffman Mtn.
Contour across and slightly down to reach the base of the West side of Hoffman. To hit the toe of Hoffman where Redtail is, it may be easier to go down slope some.
[If you are not at the height of the rock-band, it is relatively easy to contour low as well if you pick your path right. If there is a lot of brush blocking the way, scout it out, look for a break in the brush. If there is no break, work around the brush slightly lower on the slope. Stay below the aspens.]
Either retrace your steps on the way back, or contour slightly lower on the way back. Also it is possible to hike down slope from the area at the rock-band to meet up with the lower section of road. You'll lose elevation this way and hike back up some of it on the road, but it is a good hiking surface.