TBH, unless it'a professionally applied, you will get swirls. Most valeters just slap it on and because the car hasn't been prepared properly, it just looks crap.
The other thing to note is that it lasts only a few months and you should have a kit with it to "top it up".
You can get a far superior finish and protection using proper detailing products. Yes, anything over and above washing (claying, polishig) will remove the diamondbrite. Also remember it's probably worn off by now (unless it was applied within the last two months).
Depending on what you want, you can get nano-tech coatings from the likes of g-techniq and these will last over a year.
