When? Well you must wait until the 7th full moon of the year, then as the wolf cries to the eat-facing sky, the time is right...
How much? How ever much it takes.. you dont need much, a "20 sack" will disolve in less then a half-cc of water.. remember, it might be cut, so you must STILL filter!
You buy saline solution at the pharmacy, it isn't something you can make yourself.. just ask the pharmacist for a bottle of it (it's like a couple bucks for a pint) .. it's an OTC item, and if they do ask what you need it for, tell them your father is bed ridden with cancer and you need saline to flush his IV after he injects one of his "cancer drugs".. that is the most common use, however, if you say "I wanna shoot dope" they might still sell it to you!
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PAK CHOOIE UNF! Do not trust the pusher robot, he is malfunctioning, we are here to protect you..