Charcoal - Add and Subract Method

I wanted to share a little about the method I have been using to make most of my charcoal drawings lately.  It's an add and subtract sort of method.

First I print off the desired image from my computer as the size I want it.  Then I determine where I want the image to fall on my paper and measure accordingly.

Then I take masking tape, rip it to my desired length, and then de-stickafy it on my jeans, sweater, chair, blanket, whatever.  But before I stick it down against the border of my paper, I rip a piece of paper to the desired length and width, keeping one side mostly straight.  I then stick down the piece of tape right up to the border of my image, but place the paper under the majority of the tape so only a small line of sticky tape is touching the border of the image.

I do that to all four sides of the image.  I do this to help me keep clean edges.  I put the paper under the tape to protect the paper from being damaged.  It seems to work pretty well most of the time.  But, if there's better ways of doing this, I would love to know!

Once the border is in place, I shade in the entire area with a light charcoal layer and blend with my finger until even everywhere.  I then mark off inch-mark ticks on the tape and draw a very faint charcoal line connecting the marks to create a grid.  (I keep the lines light enough so that I can simply smear them out when I am done with the image).

After the grid is in place I often start just lightly drawing in the shape of the image.  I like to block most of it out before fleshing it out.  I usually measure the placement of the marks against the image I have printed and use my grid to make sure the image is as accurate as possible.

Once the shapes are mostly there I begin filling in the values.  I generally work left to right because I am right handed and don't want to smear my work, but I try to keep a piece of paper under my hand while I work too.  I like to flesh out an entire area with values and then move on to the next until most of it is complete, but sometimes jump around a lot.  Sometimes I also like to start by filling in the darkest values first.

Then after the values, I readjust if areas are too light or too dark.  To make an area white, I simply use my kneaded eraser and subtract the value. 

Lastly, I add in textures and other small details to make it complete.  Once complete, I sign it, take off the tape, clean up the edges if they need to be cleaned up, push down any damaged paper on the edges with a bone folder, and then spray with a fixative outside.

What is your favorite method when using charcoal?