
I have been all over that country, and up probably every road and nearly every Hiking trail
Verlot/Darrington area:
There is nothing that I would really consider a 4x4 trail, but there are a few nasty fire roads. I can think of 1 on the Mount Pilchuk road between the Heather lake and Summit trailheads. There are a couple other spurs up there that lead to great views but are in no way trails rather just little used roads. There is one spur off the Pinnacle lake road that is downright nasty, but passable if you aren't worried about a few scratches and what not. Same goes for spurs off of the Cuthroat lake road, Deer creek road, and Coal lake road. There are a few things mixed in there that I have seen listed as trails on various 4x4 sites, but they're full of it
I have found 4 old fire roads off the above listed FS roads that likely qualify as a moderate level trail, but they are so overgrown that I left my X at the bottom and hiked them. If you head up the green mountain road there is a trail off the right just before the pavement ends that is very nasty!!!! You will see it right next to a big mud puddle. I never made it around the first corner till I locked my rig. if you do make it around the corner be careful or you will likely roll it on the way up the rest. I backed down once I got to the sidling part, started tipping, and crapped myself

Once you get closer to the top of the Green mountain road there are a few mildly interesting spurs, however a lot of this area is no trespassing.
Skykomish/Steven/Index area:
Up along Hiway 2 there are a few fair trails that branch off the FS roads going up Stevens or index. There are also some fun areas back in the Sultan Basin so I have heard. Really though Reiter is your best bet for a bit of wheeling, and at least there you have others around if you need assistance. Just stay out of the Tank Trap on the Index Wall Trail.
A warning though. The rangers in these areas will not tolerate screwing around AT ALL. I have seen several people fined on the Mount Loop Hiway for treating the land with a lack of respect. I volunteer with the Forest Service maintaining these roads and hiking trails, and I love nothing more than dragging someone out of a mud puddle and taking their plate # down to the Ranger Station

Nobody is concerned if you want to drive a fire road, and there are some beautiful areas at the end of many, but stay on the roads and out of the Mud!
I am sure that you could con a few of us into heading up to Reiter or follow us back into the Cle Elum area in a few weeks.
Check the Nw Explorers forum for trip reports in these areas, or click the link to my registry down below and there are links to the threads at the top of page 1.