Dark colors are always a more difficult, because they require the things I mentioned. Metallics tend to hind minor imperfections better than solids, but that wouldn't be an option when painting a piece at a time.

Most colors are a mixture of tints and toners, so they would have to be mixed very thoroughly just before spraying each piece, or the settling action will seperate the tints, and you may have a mismatch. Black and a base mixing white would be exceptions.

The advantages of BC/CC urethane are many. If you think you will continue painting other projects, I would recommend this most popular system so you become familiar with using it. All colors are available in this system, where you are limited in other paint types. I just gave away a few thousand dollars worth of paint, and went totally urethane, for just this reason.