If it were me, I would use a gloss black base. It provides a smooth surface for the paint to lay down. I’ve not used the brass paint that you spoke of. These paints usually require a sealer to prevent fingerprints, and rubbing off the paint itself. Before I put any paint down, I clean the part with compressed air to get any dust off right before painting. Hope this helps
As stated above, definitely start with a Gloss Black base before painting the Brass. The Vallejo color you mentioned is part of their Model Air line and should be airbrush ready (may still require some thinning).
In my experience, metallic brass paints never really pull off the look of polished brass that well. I recommend to experiment with first applying a good chrome finish (such as Alclad, SMS Hyperchrome, Revell chrome-in-a-can, take your pick), and then after that is completely dry airbrush a mixture of mostly clear yellow with a bit of clear orange acrylic (not lacquer or enamel). This should give a pretty convincing polished brass look. But I can’t stress enough that you should experiment on spare parts first before committing to the actual kit parts.