Hardest colour to clean without a doubt, had a Golf GTI years ago, it looked lovely when I picked the car up from new, couldn't get it the same after I washed it!! Good luck, worth the extra effort IMO.
nsm3 - a cheaper solution would be to get a microfibre drying towel from Halfords. Only a fiver and it can be used instead of the wash leather - but I do a quick wash leather then finish with the towel. Although I now have Daytona G, my last Audi was a deep blue (Ming Blue) which had all the characteristics of the Moonlight Blue. It looks fantastic in all light conditions and by doing the above, I never had any spotting issues. A treatment with a synthetic wax (£20 and a bit of elbow grease) will see off most of the water deposits and save the wash leather cycle. No need for all that detailing faff.
I have used microfibre cloths for years and they are great at drying the car without leaving spots or runs. Wilko sell them 3 for £2. I tend to use a new one each time and throw the old one away. I also use one for for the interior glass as it brings it up streak free.