black T cut wont, it is just for scratch repair, it is not a wax or polish
T cut is effectively a filler....but only lasts for a short while as it fades and the cut will come back (unless a very light surface scratch)
I have a black Leon also, best wax I have found is Victoria Concours wax, good for dark couloured paints and also lasts very well under weathered conditions and brings up a great shine
Polish, if you want something easy to use is the autoglym polish or Meguiars quick detailer
I would also recommend using Meguiars **** class shampoo, cleans really well and leaves a nice shine to the paint even before the polish or wax is applied