I am husing Humbrol enamel paints in small cans, diluted 1:1 with terebenthine or the Humbrol solvent: two thin layers with more than milky dilution, and drying time of 8 hours between. The first layer not yet opaque allows also inspection of any left defects on surface. Seems better than acrylic water based on metal. Diluted layers also do not hide fine details of the scupture, if one pay attention on application to avoid leaving recessed lines or holes to be softly brushed out during the application....
Brush flat, soft and fingers light on brushing, well crossed rapidly (fast drying)...