This route is pretty much straight forward: it is mostly made of the New Millennium Loop Trail and is using a nice way to get to it. It goes for around 14.8 miles and elevation gain is about 2,831ft. It can be done clockwise or counter-clockwise, but is better counter-clockwise if you are somewhat sensitive to height. Access to the actual loop is best from the Bark Park at 4232 Las Virgenes Road, Calabasas CA 91302, that has plenty of parking, a porta potty and a water fountain. There is also some access from the Mobil gas station on Las Virgenes Road by the 101, and from the end of Calabasas Road.
From the Bark Park go up the Bark Park Trail. After 1.2 miles make a left or a right on the New Millennium Loop Trail depending on your choice to make it clockwise or counter-clockwise. There are signs pretty much at every intersection and the trail is fairly easy to follow at road crossings. The loop is made of a single lane trail for the most part and a 0.9 mile piece of the Gun Club Road. It goes around the gated community of The Oaks, home of some celebrities.
You can get a nice view of some of these homes from the top of the switchback on the south side. The loop has some very nice spots, but can be difficult at times when it has not been cleared. It is best to use it during the winter when the grass is low, and to avoid it for sure right after the rain allowed the black mustard to cover it. To make it easier it is best to ask around or check reports if the trail has been cleared.
Christophe did you do this clockwise or counterclockwise from the split you talk about at mile 1.2?