If you're not sure where to start with sketching, or with the Mellish Technique, this might help. The picutures in the Mellish article where done by reproducing black and white images of the selected targets. They were also images that weren't too far from how they appear in the eyepiece. More detailed images can only serve to confuse.
Have a look at the image and the sketch development. This will give you a very good introduction to using this method. Then at the eyepiece, you are leaving the guess work out of it.