This is a long ride at high altitude. Most people will do this in 3-4 days. There are many places where a 4x4 can meet you for luxury camping and make this an epic MTB trip!
Starting in Telluride, you might as well enjoy some free vertical (you'll do plenty on your own later!), so take the free gondola up to the Prospect trail. This a a beautiful cross country singletrack with no major climbs and tons of fast descents, partly in the ski area, and partly in what feels like pretty remote wilderness (though it's not).
Once back in the ski area, head down various trails (use the mobile app to find your way, it's confusing) until you get to the Galloping Goose #499
. You'll now follow that for 18 miles following the historic rail grade along easy trail with superb scenery. You'll probably want to camp somewhere before this ends. There are several good campgrounds around Trout Lake.
Head up the East Fork Trail #638
, which actually descends for a while before starting a long, somewhat techy ascent up to the Colorado Trail. Parts of this are beautiful, parts are pretty tiring. Push through. Good camping at Bolam Pass, which can be reached by 4x4.
You're now on the marvelous Colorado Trail - CT - Segment 26: Blackhawk Pass! This is a big day and you'll reach the high point of this ride (12,000') at Blackhawk Pass. The trail is remarkably rideable (if you've got the lungs!) and passes nonstop stunning scenery. Enjoy the huge long fast descent and perhaps find camp somewhere.
Continue on the Colorado Trail to Hermosa Park Road 578
All of the Hermosa Creek drainage is closed due to fire in the summer of 2018. As an alternative finish, you can stay on the CT (a long ways, quite hard), or take Salt Creek Trail #733
down to highway 145 and get picked up on the highway.