My first peak hike and have climbed the Rhino many times over the years with many friends.
Some prefer to sleep over at Pillar cave and make a 2 or 3 day hike of the Rhino but it is easy enough to do in a day. First assent (aged 12) it took 13 hours (return). Fastest route was about 6 hours (return).
The route is quite gradual until you pass Pillar cave and then gets steep going up Mashai pass. Can be tricky in winter when the river freezes over. Once you get out of the valley on top of the Lesotho Plateau head right and back along the spur about an hour before reaching the summit.