Interesting thread this and very useful for my experiments.

I separated out the sensitizer and just coated with the ammonium iron(III) oxalate. Very quick exposure times, then developed in a solution of Silver nitrate and tartaric acid. I imagine this can be reused for quite a while but will still be more expensive than adding it to the coating.

Bonus is it works - very nice dark tones. I developed after in a solution of Rochelle salt and Borax although I suspect this isn't necessary.

Here's an example --- - more testing needed especially in terms of the right neg. Step wedge testes definitely needed