Any chance of getting a 20tank cheapo tank with cheopo flourescent lights? Use the HOB
skimmer there and a few of the better pcs of rock for an instant cyle. I'd use 50% new, aged SW
(24hrs at least) and 50% old water.
Then, like mentioned scrub and recycle the rock. Keep it dark for a week with a power head and hopefully ambient heat. If not, a small heater. New test kits!
Then as you add new fish, you've got a ready made QT tank. Treat the 20g rock and add to the other rock already done. Move the fish.
And be sure that nylon brush is a brand new one without any metal. It'll be your tank brush. I like the kind with the round or oval surface with a longer handle.