Tightening up with Mixer brushes
To sharpen details I use my Mixer brushes. I turn on ‘Load the Brush after Each Stroke’ and ‘Sample All Layers’. I tighten up areas that are unrefined and blend colours so they feel more natural. I reduce the Opacity, which recreates traditional painting where, as paint dries, layers underneath show through. Once it’s less opaque, I create a new layer and paint until I’m happy.