well I will give my ten cents since I used to detail cars many moons ago. Still do but just limit it to friends and family and of course my car.
Its tough where to begin. Lets assume that you just washed your car and dried it. With a CLEANhand GENTLY slide your finger tips along the paint. The paint should be smooth as glass. If you fill something with your finger tips then you have contamination and yes it needs to be clayed.
Clay, which for most "Synthetic Clay" is a special polymer substance that acts as a friction device to gently pull those contaminants off the paints. Examples: over spray, fall out, rail road dust, sometimes etching etc. Claying comes in different hardness as well. To keep it simple, lets just say you use the "Mothers" Clay kit you can buy at your local Wallyworld (which is decent by the way, and is considered a medium clay).
To clay the GTI would take several hours to do it right. You just mist a lubricant onto the surface, gently wipe the clay back and forth. mist again, wipe dry and feel. just keep doing it till the car is done.
The reason this is important is you dont want to wax over contaminants or put a sealer over them. You want to polish or seal the paint not the dirt on it. So claying is a crucial role to have the product your applying BOND to the paint. Doing so will lengthen the durability of the product your using.
Everyone has their brand they love so I wont go into brands to use, just use it often. If you live near rail road tracks, a big city with pollution or in High UV areas wax or seal monthly, claying when needed. If you are lucky to live in a nice clean low UV area, I would do it every 3 months. Dont believe the hype of a "Once a Year Car Polish" from ANYONE its a total crock. Protection begins to decline after day one. If you want to keep it up, keep putting it on. Better to have as much on the surface protecting that nice BASF paint job then not enough and a nice Bird Bomb just etched into your paint. So more frequent is always best in my book.
Lastly, you have a nice car, you paid bank for it, so dont get lazy and not wash and wax it. Just get up, and do it. Your car will love you for it, and the exercise will do us all good anyway...
Enjoy.....any questions on what to use, just PM me. Dont want to start a brand bias war on your Post.
Jeff