I made the sculpt low-poly (approximately 10000 tri) so the character could be used in a game (Fig.04).
I extracted the complete map, occlusion map, diffuse map and normal map by using the Render To Texture function. I then made the textures, but I'm not going to go into detail about that here.
I wanted to make a more detailed normal map, so I used the additional bump option. I put a bump map in this slot and then extracted the "bump-normal map" using low-poly on low-poly (Fig.05).
If you compare this with the first normal map, you can see that the second normal map includes the bump detail. If you think this process is too complex then you can use a normal filter in Photoshop, but I think this process is much better (Fig.06).
It is important to improve the quality. Here is low poly model that I applied to the final normal map