Today I did some experiments with my homebrew Reducer with Ammonium Thiosulfate. As Ian said start with 10% stock solution. With this in mind I made some testprints. Started with a very diluted version with 2,5 ml Solution A and 12,5 ml Solution B at 1 liter water, souping the print for 30 seconds was quite right. This gave me an 0,05 density reducing in the highlights just enough to give it that sparkle I needed.