At the suggestion of Mr. Eugenio Sinatra I have experimented with the Chromoskedasic Sabattier Technique. As far as I know, the two solutions are only available at Freestyle. The chemicals are cheap, but the shipping costs to Europe are much more expensive than the products. That´s why I made my own stuff for me and my European customers. Most probably my concentrates work somewhat different, but the mode of action is the same.

Stabilizer: Ammonium thiocyanate (mild fixing agent)
Activator: Potassium hydroxide

When both solutions are mixed and a small amount of developer is added, fixing and developing take place at the same time. The more developer and/or activator, the more color will be formed in the low exposed lights after turning the light on and a following development of the lights in the 3rd bath (activator only) by visual inspection.