Hi Stephen,
recently treated my Jag to its bi annual clay bar treatment. If you clay bar your car, you won't need to use T cut unless it's to remove stubborn scratches and then make sure you give a couple of coats of wax polish and sealer to protect the paint. The Clay bar idea is to remove stubborn gritty surface and restore clear coat to near to original condition
pic below and link to a great detailer on YouTube, , cheers, Andrew