The 10 trail encircles the ridge that forms the heart of the Parco Campo dei Fiori (Field of Flowers Park). The northern section from Orino to Brinzio is now signed as 310b and gets a lot less traffic than the southern section Campo dei Fiori Sentiero 10a
Leaving Orino, the trail quickly becomes an easy doubletrack as it winds its way through the dense forest (no sign anywhere along the 10 of any kind of field of flowers), occasionally with wooden bridges over some small streams. There is a little bit of gentle climbing in the first 3 km (1.9 mi) before you reach a clearing just before reaching SP45.
Then the trail turns south towards the mountain, and there is a small climb. After about 1 km (0.6 mi), you'll reach a cemetery on the left and some light industrial buildings. Just before you reach the SP45 for the second time, there is a small trail that goes down to cross a stream (Rio Caprera) with a pretty waterfall and with a little chapel on the opposite bank just before the path joins SP45.
After a short section along SP45, 10b turns south to climb 150 m (500 ft) up the side of the ridge in only 1.2 km (0.75 mi). This is a difficult, narrow singletrack so many mountain bikers will (gasp) take the easier SP45 (paved provincial road) to Brinzio. If you do opt for the singletrack route, you can anticipate a fast, steep descent into Brinzio.
Note that at the point where Sentiero 10b leaves SP45 to begin this long climb, there are some singletracks heading parallel to SP45 that appear enticing. These lead to some abandoned buildings and shortly dead-end. So your options are SP45 or the difficult climb.