This material is in addition to the procedural wood material wood setup. So you need to add the below node setup to your material.
Step 1: Select object.
Step 2: Again we use a dirty vertex to control the transition of materials. the more faces you have to work with the smoother the shading from light to dark. Topology will effect the balance of light and dark, so if you don’t get the desired effect then you can always manually paint some light and dark.
Dark patches (black): will mostly be covered in paint, with small random gaps.
Mid-tones(shades of grey): paint layer breaks. The wood grain revealed. The edge of the paint is slightly paler.
Light tones (white): pale scuffed wood grain.
Step 3: Add this to your nodes. I recommend playing with the settings to see how it fits together. Change the values to increase or decrease the scale of the flaking paint effect.
Note: This is how to add it to the existing wood grain nodes.
Step 3 1/2: For greater variety add in some random colour, but not too random. Control the variation with the “Hue Saturation Value Node”. Just plug it straight into the paint layer colours. Play with these settings.
Step 4: Make something awesome and let me know about it. (Because I’m needy like that)
Note: Really play with the settings. by adjusting a few settings you can get some really nice effects for other materials. Like warn paint on metal.