If you did use T-Cut then you will have removed the supargaurd.
TBH it is a bit of a waste of money.
Applied corectly after a correct detail you may get ok results but half the time stealers just slap it on. You are better off buying some AG SRP and extra Gloss and put the other 300 notes in your sky rocket.
Have a look at other threads on here about detailing or look at http://www.detailingworld.co.uk