I've always either used Autoglym or Meguiars products on my Skuds.

When I bought my red vRS a year or so ago I had to remove the deposits ground into the paintwork with Megs clay and detail spray as the car had been sat on a forecourt with passing traffic making it terrible to polish.

Well...my Superb is exactly the same. I polished the car with NXT wax and after copious amounts of elbow grease IMO the car only looks passable.

I've run out of detail spray to get the gritty deposits out of the paint and my local car shop no longer stock it. megs online charge

For prep, definitley clay. I like Sonus clays - I think the grey would be ideal for you. I use Megs Last Touch diluted 1:1 as lube - keep misting all the time as you work the clay. I bought a gallon bottle for £20 odd, and the proper sprayer for about £2 - all from Clean and Shiny - Perfection in Reflection totally recommended. The Last Touch can be used as a quick detailer inbetween wax applications.

After, use a good polish with some fillers. Auto Glym Super Resin Polish is great for hand work, and masks swirls nicely, whilst removing the lightest ones. This gives the best results for working without a rotary polisher or random orbital polisher.

Then use a glaze if you like - not sure what is best for dark colours - but Vanilla Moose Hand Glaze is great for lighter colours. This step isnt essential - but does add to the depth and wetness of finish.

Then seal. Again, not essential, but means you wont have to wax as often.

Then just use a decent wax... Nattys Blue is superb for dark colours like yours.