Does a fingernail catch in the scratch?
If it does it will NOT polish out.
Assuming it passes this check...
Personally I would attack it along the scratch with farecla G3 then G10, then polish the bonnet with blackfire using a DA polisher, followed with Zaino Z2
You have to be careful with black, or it will look like you took the edges off the scratch with a Brillo pad.
If you want a quick try at DIY, the easiest product is meguiars scratch X from halfords.
All you want to do is soften the edges of the scratch so that it doesn't reflect light, so it's still the, but you wont see it.