I have been reading Leicaphilia (http://leicaphilia.com/) for a few years. The other day Tim Vanderweert noted that he uses Diafine to develop his black-and-white film. I shot these images to test a used lens I bought from KEH.
So I ordered it from Glazer’s Camera in Seattle for about $22.00, which is enough to make up a quart of each of the 2 part developer.
You do not dilute it; you return it to the original container after use. This can go on for up to a year, and you only need to replenish any used in development.
In the Northwest, we have dark winters with little sunshine. Diafine adds speed to the film, which might help shoot on dark days. These images were shot at ISO 800. They were developed in both solutions for about 3 minutes each. I shot a roll of tri-x 400 today at ISO 1600. We will see how well Diafine does.