Well...over the time I developed techniques, however I bought new materials and that help a lot. I use fine art cretacolor pencils and the mechanical pencil 0.3 pentel. I made use of stum/blender to blur and make the smooth areas , the hard eraser pencil have a function similar to the stump/blender, it helps to spread the graphite strong and without erasing.
Take a look in other works and look the comments, usually I give various tips to people who ask me
I hope it help
sorry for answering in English, my Spanish is not so good: peace: