Clearly, you don't need a full studio or an easel or even the right lighting, clearly! ;)
I think I just taped the paper to a piece of MDF and went ahead with a piece of charcoal, a cloth for smoothing edges, and an erasure.
I kept the reference pic nearby but didn't do any kind of grid transfer technique to keep the likeness, which in hindsight probably would have served me well, but I remember at the time feeling strong enough about it. Probably because the lighting and values on the photo were good enough but with very low detail. This combination of strong values and low detail was perfect for forcing me to see the important parts of the image and carry that through to the drawing.