This 8.5x11 recent drawing was done with a set of Prismacolor warm grey markers in about 2 hours.
I recently purchased a set of warm gray Prismacolor markers and a colorless blender. The markers cover the value range from 10% dark to pure black. If you need an explanation about color value see this post
here. To make the drawings I just used a home made value checker to identify which marker best matched the needed value in the reference photo, and then simply used the appropriate marker where needed. It does take at least two passes with the marker to fully saturate the paper so that you can achieve the intended value. It is possible to make large areas of relatively even tone with these markers. The colorless blender allows you to lighten passages and blend tones together. I've read you can also blend with just a brush dipped in rubbing alcohol or Everclear. Using the actual markers, I made a little hole -punched cardboard value checker. The value checker is pictured here with the reference photo.
The reference photo was used with permission.
Here's a few other drawings made with these markers:
Here's a marker drawing done with just a black Sharpie, a gray Bic marker, and the Prismacolor colorless blender:
Here is a picture of the markers used. In artificial light the completed drawings have a slight sepia tint.