CMB shared an interesting tip with me the other day in a PM, and he said it was OK to share in this thread:

Quote Originally Posted by CMB
It seems you've located a source for Hardener No.3 (Diazidostilbene Sodium Sulfonate) and the next thing to do is figure out how to use it.

When testing it, I recommend that you keep in mind Kosar's statement that it can be used in a similar fashion as dichromate. Thus, if you are used to making up a three percent PD solution and tray soaking for however long, do the same with the Hardener #3. Be careful that when mixing it with water, you do not allow the temp to exceed 85F. Try not to change anything in your technique except substitue Hardener #3 for dichromate. It will be a good place to start...
Thanks, CMB!