I think it is very interesting to use 3D software to make images since my sister works as follows AFAIK.
1) draw manga on paper using pen & ink
2) scan the images into computer
3) add screentone effects using photoshop
Maybe I will mention the possibility of using 3D software to my sister.
As Donnageddon said, as long as you tell us your story, I guess you are free to use whatever tools that suit you. Also everyone will get better by practice and such improvement is also very important aspect in life, I think. If someone can achieve everything at once, it will be really boring world, isn't it?