Agreed don't touch this paintwork with T-cut. To be honest even if you did it's unlikely to have the desired affect as T-Cut isn't really designed to work on lacquered paint. The lacquer on Audi paintwork is extremley hard and stubborn that even the detailer I use complains about. If it's contamination on the paintwork then use of a claybar will almost certainly remove these marks.I won't T-cut anything. Start by using a Clay bar, or a light polish but nothing as aggresive as T-cut.
You'll find all the detail you need on how to clay here http://www.detailingworld.co.uk/forum/showthread.php?t=4829&highlight=clay and here http://www.bilthamber.com/autoclayhowto.html
Claying is a simple job you just need to remember to always use lots of lubrication so not to burn the paint (treat her like a lady and you'll be fine )When finished don't forget to add protection as just like T-Cut claying removes all waxes and protection from the paintwork.
Bilt Hamber supply well priced and user friendly products that IMO will give fantastic results for a job like this. You can buy their products directly off their own site. Personally as well as their clays I use their Auto Balm for paint protection instead of wax, I put Ess5ive onto this product and if you search this forum he's posted some pictures of the fantastic results he got. There is also a Bilt Hamber section on the Detailing World forum for further info.
Time scale wise for the area mentioned you're talking no more than half an hour to complete. I personally now use a detailer 3 times a year and top up the autobalm protection myself claying any small areas that require it but as the car is garaged it rarely needs any other attention.
Of cause if you don't want to do it yourself or haven't go the time there's always a detailer lurking on the Detailing World forum willing to take your money.
Just don't use that T-Cut if you value your car!