For my suggestion on something for black cars that can hide some light scratches and is very durable, try GTechniq C2. I've been using it for a year and it always looks great and lasts 4-8 months between applications. Usually long lasting sealants don't have fillers and stuff with fillers don't last long. This does both. It is mostly sold in the UK but I've seen it at some US vendors. Kinda pricey at $90 for a 500ml bottle but that bottle will last you a good 5 years or longer. You can spray onto the car to apply.. but much better to spray into applicator to apply so you don't use a lot of product.
It's great for soft finicky paints like Jet Black. I swear I'll never get a Jet Black car ever again...