Keep in mind ....

... that always when we want to make a new mold the most important thing is our original piece to be clean and as shiny as it can get
Here is an example with a metallic part

Here it is in its original condition

Then you can clean it with a brush (than you can use with an electric tool or manually )
Here it is during the process
 (Sand blasting would be a good idea but only with a very thin powder otherwise it will leave a surface with large pimples not good for our mold ) 

Then you should sand it with some wet sandpaper and at the same time spray it with WD-40 or another penetrating oil

After that you must follow the buffing procedure so it wont stick to the mold and when you are done you are ready for your carbon piece

Good luck