For an artist who loves to work with smooth, flowing paint and vibrant colors, and has ample time to complete a commission, the best choice of material would likely be acrylic paints. Acrylics are known for their versatility, vibrant colors, and ability to be thinned with water for a smooth application. They also dry relatively quickly, allowing for layering and blending techniques.
If the artist is looking for an even smoother texture and extended working time, they might also consider oil paints, which have a rich, vibrant color payoff and a longer drying time, allowing for intricate blending and manipulation.
In addition to the choice of paint, the artist could use a high-quality canvas or panel to provide a good surface for applying the paint, further enhancing the smoothness and vibrancy of the artwork.
Ultimately, the choice between acrylics and oils will depend on the artist's preference for working time and finish.