Stitches in Substance Painter can be customized in shape, length, and distance. They can be created or imported from Photoshop using a mask map. To find stitches, activate the stitch button and search for brushes with the orange symbol. Adjust brush settings in the properties panel, including size, pressure sensitivity, stroke capacity, spacing, and follow path options. Stitches have features like color, gap, and fabric fold. Make adjustments to color, intensity, and type of stitches, such as creating double stitches or changing thread thickness. Use the lazy mouse feature to prevent stuttering strokes.