I am a hobbyist detailer for my SLK32. I know what it's like to want perfection in your paint. As a result, as my gf will tell anyone, I am O-C about my car's finish and cleanliness.
LSP's (Last Step Protection, as termed by the pro detailers for wax or sealant) are a very personal choice. Just like what wheels you put on your car, everyone has their own preference and tastes. So to try and answer your question, there is no 'best' wax for your car, it's only what you prefer the most, easiest for you to apply and take off, lasts the longest for your driving and climate, etc.
Yes there are some crappy waxes out there, and there are some that are so ridiculously overpriced you can't imagine what makes it worth $2000 a tub
What I can say for sure is that it really doesn't matter what LSP you use on your black car if your clearcoat isn't ABSOLUTELY FLAWLESS to begin with. If there are imperfections, the wax is only going to protect that imperfection!
Think of wax as saran wrap - it just protects what's there.
To get that perfect clearcoat to begin with, you will need a polisher (PC7424XP is a good and safe choice) And to take out imperfections such as your swirls and holograms, you will need the correct polish/compound combination for your paint.
When I started researching the polishers, I was afraid (who wouldn't be, taking a powered tool that spins to your baby's paint!) I saw this video on YouTube from the "Junkman" @ Adams Polishes -
YouTube - How Safe is the PC 7424XP - Part 1 and
YouTube - How Safe is the PC 7424XP - Part 2 and it convinced me that this was the polisher I was looking for.
Once you get your clearcoat perfect, then it's time for the LSP. I personally always end up reaching for the Menzerna Power Lock (MPL, as they call it). In my experience, it leaves the absolute slickest finish and looks the shiniest on my yellow SLK. However, for a black car, you can definitely experiment with different waxes and sealants to see what works the best for you.
I bought my detail kit from detailer's domain (
www.detailersdomain.com), who is a sponsor for the SLKWorld.com forums which I am an active member of. I got their Porter Cable 7424xp kit with Menzerna polishes (
http://www.detailersdomain.com/theub...es16ozkit.aspx). I decided to go with Menzerna's compound and polishes due to the fact that it's what Mercedes uses at the factory for finishing off a new car off the assembly line. Their final polish is specially formulated for Mercedes' clear coats. I'm not sure if Crossfires use the same paint as Mercedes but if they use the same scratch resistant ceramic clear coat, I recommend Menzerna.
I really like Adam's products for everything else - Tires, trim, rubber seals, interior, leather, carpet, windows, car wash, etc.
There's a discount code for 10% off entire order, code "MB".
Some detailing forums that places that I order my stuff from, they may give you some more info:
Detailing Bliss Forum - News
www.detailersdomain.com
www.adamspolishes.com
www.adamsforums.com
We Are Car Care -- Car Wax, Car Polish, Auto Detailing Supplies, Car Buffers & Car Accessories Store
A forum member on detailingbliss.com states in his signature, "Black cars are not a hobby, they're a career." as they are the hardest to achieve a flawless finish. Good luck on your detailing!
Jae