Transactions, in one case, were made through exchange of empty white canisters in exchange for filled canisters. Jem'Hadar ships approached the facility and requested to be resupplied with new canisters. The ship then beamed down a number of canisters from its cargo hold and was given the same number by the facility.
In 2374, three months into the Dominion War, Starfleet Intelligence discovered the location of what they believed to be their main storage facility located in Cardassian space, adjacent to a dark-matter nebula. Admiral William Ross gave Captain Benjamin Sisko and his crew the mission to destroy it. The facility in question was located on an asteroid that was protected by a security net.
Using a Jem'Hadar ship they had captured a year earlier, the former crew of Deep Space 9 equipped one canister with ninety isotons of enriched ultritium which would be detonated with a timer attached to it. That canister, along with eighty-three empty canisters were beamed down and the facility transported full canisters to the ship. However, the security net was raised and the facility ordered them to "stand by". The crew contemplated punching a hole in the security net, or even disabling the net's power generator, but they did not have enough time to do either, and the timer detonated the ultritium seconds after, earlier than set, triggering a large explosion. As the ship moved away, a larger explosion destroyed the rest of the facility and the asteroid it was built on. (DS9: "A Time to Stand")
The Federation heard rumors of the establishment of a new facility somewhere in Sector 507 in early 2375. Weyoun 6 later confirmed the rumors were true, telling Odo it was in the Pelosa system. (DS9: "Treachery, Faith and the Great River")
The Son'a had a ketracel-white facility in an outpost on Devos II. The Federation became aware of its presence later in 2375, forcing Weyoun 7 and Damar to divert warships from pursuit of the USS Defiant to the facility to protect it. (DS9: "Penumbra")