The marshall's five bottle kit that I use has the following labelled tones: neutral black, brown, blue black, selenium brown, olive. Spotting is a lost art, and it is very difficult to convey the appropriate tone mixing techniques that are required to spot the various warm, neutral, and cold-tone b&w fiber papers still on the market. Each manufacturer's paper responds to marshall tones in different ways. I would suggest saving all your less than desirable prints, and processing them to archival completion, as you would with your keepers. Use these 'bad' prints to experiment with your marshall toning efforts. Use a palette of various toning dilutions for each tone in each bottle. You will have five palettes in front of you. Assign a fine 00 brush to each marshall tone palette and never interchange the brushes. I like to let my various dilutions in each palette evaporate and dry, as I then re-wet the different assigned spotting brushes to pick up dried tone as needed. For your first experiment, simply place straight-up undiluted tone from each palette on the white border of a 'bad' print. Then place your varying diluted tones adjacent to the original undiluted, for each of the five marshall tone palettes. From these first efforts on the white border, you should clearly see just how each separate marshall tone responds to your paper's white base. I have found that most papers require mixing of different marshall tones to perfectly create a spotting match. And this is where the discussion gets too complicated for the patience of most forum readers. But as noted by a previous poster, if you are working with a warm tone paper, the marshall olive bottle tone will need to be blended with a bit of neutral black tone, and then this blend will need to be diluted, in order to match a paper like ilford multigrade warm tone. good luck.
