I've been messing about with a trio of pens- the Pentel Hybrid Technica and 2 Pentel Pocket brush pens(PBP), one with black ink and the other with gray. It's been a great combination. For the image below I looked up images on Flickr's Commons page. I happened upon some images from Florida's Archives of various southern ment from the early 1900's, some of whom were Civil War Veterens. I particularly enjoyed this guy.
I started roughly sketching in his face with the Pentel Hybrid Technica (review to follow.) I looked mainly for the large shapes of light and dark, blocking in the dark areas, leaving lights alone. I looked for the edges of things like his eyes, dark shadows, and hair. I used the pen quickly, spending no more than 5 minutes on this part of the sketch.(If I had been doing this a year ago I'd have spent about 10 to 15 min and gone much more slowly.)
After I'd blocked in the stuff I felt was important I put down the Technica and switched over to the PBP (pocket brush pen) filled with Omas New Gray ink. I was able to quickly put in the areas of lighter shadow and then build more layers upon that to create more darks. I can't over emphasis the virtues of this ink for sketching- the fact that it starts out as a nice silvery gray and gets darker and darker with additional layers is fantastic. It is not light fast, but is perfectly fine in a sketchbook.
After I was happy with the level of shadows I'd built up with the gray ink I grabbed the PBP with black ink and started to darken the darkest area and add some additional texture with it. The eyes, hair, and shadows were all deepened with this pen.
This pen combination is great, the Technica is great for quick little sketches, it handles being treated roughly quite well. There are some areas where the gray ink will lift the technica ink if I've done really heavy scribbles that overlay one another. It's not noticable in the finished sketch. If you wanted to sketch in pen and ink, these are all the tools you'd need.( I mean, you could add a fountain pen or two, just in case you want another line….)