I hate to tell you but you purchased the wrong color for filling swirl only protocol. Black ( I have 3) requires meticulous care. In one year with routine washing even with the best tools, shampoo and technique will still leave your car appearing greyish because of the numerous unrepaired surface marring. The black basecoat will be optically diminished by trying to present itself thru all the marring, filling and protectant.
If the marring is very minimal try a paint cleanser like Clearkote Vanilla Moose, P21S GEPC or Menzerna FP. There is a Sealer Glaze by Mothers that's rather good at filling swirls which is non-abrasive but I would suggest a carnuaba for protecting because of all the fillers and oils in this product. Two of my black vehicles are rarely driven. Why? Black is not a daily driver color IMHO unless it is a expensive paint found on hi-end vehicles (Lexus, Mercs, Audi, etc).
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