Grab yourself some Seachem Matrix, put it in a bag in your sump and leave it there to populate with good bacteria.
If/when you need to get the QT going (esp. in a hurry) just move the bag of Matrix into the QT, in the HOB if it fits, or in a pinch, just in the tank (in the bag).
This will provide "instant" biological filtration that is already established and help prevent water quality issues in the QT.
If you find evidence of disease and/or medicate, do not return that bag of Matrix to your DT, simply discard the Matrix when you're done, if you're taking down the QT, and place a new bag in the sump for next time.
If you just QT and everything goes fine, when you take the QT down, you can return the bag of Matrix back to your sump to keep it live and ready for the next time.
HTH
Jenn