There seem to be several ways of finding a trail up Job's; here's one more.
(1) Take 89S from US50 to forest service road 051; 051 is also on maps as Willow Creek Rd. This is a little trickier than it sounds because 051 is not marked as such. Or marked in any other way, for that matter. 051 will be on your left as you head south on 89 just beyond Luther Pass, and there will be a stop sign facing away from 89S - that's pretty much your only clue. If you hit the 88/89 junction, you've gone too far.
(2) 051 is an unpaved, ROUGH road. Continue for several miles until you see what appears to be a true, well-traveled side road on your left (at N38 50.100; W119 53.525). Turn left onto this road.
(3) Continue until you reach the end, where the road kind of cul-de-sacs. Park.
(4) The trailhead is behind what appear to be several boulders blocking an old service road, and the trail becomes quite clear.
As you head up the trail from the trailhead, you'll meet an intersection (.29 miles) where you must choose to head either left (down) or right (up). Bear right. The trail is well-defined, and as you increase your elevation, you'll see Freel and Job's Sister on your left.
You'll reach a vista, with some interesting rock outcroppings. As you emerge through a small copse of trees, you'll see Job's Peak on your right. There is an obvious trail to the top.
Pay attention to how to get to the summit trail from the vista - because there are a few ways to get to the summit trail, the trail breaks up a bit and becomes ill-defined in sections. Learn from my mistake.
One nice thing about this route is that someone has marked the route by tying neon pink ties to several trees.
Standard stuff; it's not a terribly long day hike but there's lots of exposure.