I won't speak for Ted Rice (have known him since 1978) or Bob Nugent (known him since 1980) BUT have watched Bob make ferric oxalate with steel wool- he got the formula from one of Dick Sullivan's priceless issues of LUMEN. Works like a top if you can draw a good vacuum. Makes great ferric oxalate, at least for kallitypes (my application) but no better than B&S version which I've bought since 1984.
Rudiak had a perhaps unique variation on making ferric oxalate which he developed about 1998. It had some interesting ramifications on speed, color and tone. I watched John make it once; he died about ten days later. Did I take notes? Heck no- he'd always be there to ask...