If you want to achieve a high level of polish, it’s really mainly a matter of patience. Make sure you use appropriate brushes for different surface types, such as hard-edged brushes, soft-edged brushes, custom brushes with custom settings for scattering, which is very useful for textures, as well as various speckles or textured brushes. Know exactly what type of surface is on everything and then render them as intended.
You need to also know exactly what edge-type you’re trying to depict. Not all edges have to be sharp. Some would be soft, or quite blurry, depending on what you’re depicting. Edge types generally should have logic to them, such as your main focal points having sharp edges and contrast, and areas that you don’t want to compete with the main focal areas would have soft or lost edges with low contrast. The hierarchy of your Z-depth also plays a part, just like how camera lenses focus on a focal plane and everything gets gradually softer the further they are from that focal plane.
So with the above in consideration, you will see that there are a lot of inconsistencies in your image, and if you simply tried to be more consistent, you’d be able to take the image a lot further and solve most of your problems with polish.
