I always break down my QT between uses, just because if the tank is up and running I know I'll fill it then need another QT.
When I need a QT. I use an established sponge filter, NEW water (old water is just going to bring in pollution), bare bottom and a decent size chunk Of LR that I am willing to sacrifice if I need to treat with any reef-unsafe medications (aka an ugly rock out of my sump). I keep new water handy in case of spikes but havent had a problem using this route yet. feeding VERY lightly is key when you have very little biological action.
the simple fact is when doing it this way there is nothing to cycle.... everything already has an established coating of bacteria (except the glass), you'll only have problems if you exceed the amount of biological capacity your one chunk of rock and foam filter are capable of houseing. AKA BIG fish + small rock = bad news.
I almost forgot I dont run lights on the QT for fish ambient room lighting is more than enough, it helps de-stress the fish. I DO use lighting when QTing corals.