Yes mate, that makes sense.
Are you talking about actual scratches EG where it's been caught against a bush or are you referring to the general swirl marks on the vehicle?
G3 Scratch Remover (green bottle available in halfords) is quite good for genuine removal of localised scratches.. It feels very gritty but it's a diminishing abraisive so works down. It's hard work but would get the results you want.
The effect of the Blackhole will be the same however due to the colours of the car and the way in which a black car reflects light versus a grey car or a pink or an aubergine car, may appear different.
Ditch the Poorboys and get an actual proper polish or compound on there ;)