I've done this route many times, last time being in March 2018. In Laredo Bridge # 2 is right at the terminus of I-35. Once over the bridge turn left and follow the Rio Grande to a sharp dog leg that will take you to a pretty fast and organized TIP & Tourist Card center. Others here will suggest Columbia but I prefer #2.
The roads are good, one can take the toll roads or free. There's a fast, new loop to avoid Torreon's traffic and an well established toll road to avoid getting too far into Monterrey.
West of Durango there's the fast and easy toll road to take you to the coast, and an amazingly well maintained free road that has hardly any traffic. Along the free road not too far from the Durango end there's a government campground - it's usually gated but when we rode past on Easter week it was open and busy with campers. Maybe someone else here knows more details about this campground.
It's about 700 miles, give or take. The free Mex 40 west of Durango passes through incredibly scenic mountain ranges, Keep your gas tank topped off on this stretch, services are limited on the free road.
