IMPORTANT: The juggling torches are not soulbound.
You can throw them over to a friend, and you can put them in your guild bank. This makes it quite easy to share your torches after getting the Torch Juggler achievement.
Have a group of 4-5 people complete the torch-juggling practice quest at one of your faction city bonfires, so that all are allowed to catch the juggling torches. This will reward each of you 5 torches. Each of you should keybind your torches to make them easy to spam, then, gathering in Dalaran, throw all of your torches over to one person by tossing the torches to them, targeting them with the green "aoe" type targeting marker. It is important that the target-player not move, or else the torch(es) may be lost. Edit: alternatively, you can just trade them to that player... ... ... hush, I like throwing things!! To quote the little fire elementals in Nagrand, "Reth reth reth!!"
Once one player has all of the group's torches, they should spam the torches at their own feet (targeting themselves, basically). Just keep spamming the button, and the torches will be juggled. Eventually, with enough spamming, they will get the 40-torches-in-15-seconds achievement, and they can then throw all of the torches over to the next person.
Once each person in your group has the achievement, you can put them in your guild bank for someone else to use, or toss them off to someone else. The new recipient MUST have completed the first torch-juggling quest in order to be able to catch them, however!
Mind your leaves :) You can toss torches while in cheetah form, though, so you may find travel form useful while trying to chase the dailies' torches around the screen!