To hold the octo:
1) Find a D-ring on your BC (low on right chest strap for me).
2) Pass the one eye around the D-ring and through the other eye of the Snorkel keeper and pull tight.
3)Take the free eye of the snorkel keeper and stretch it over the mouthpiece of your octo so that the eye is around the neck of the octo mouthpiece.
Its now secure, pulls away readily for use, you know where it is, a panicked diver might see it first, works on any octo and rental rigs, dosen't drag in the sand and it cheap and readily available world wide.
Those keepers are pretty usefull things. I always carry a spare in case my dive buddy did not bring one.
--DP