Why not embed the lubricating particles later, when you oil the phosphated steel parts?
First make a completely standard phosphatation of you steel. Then, use a graphite-loaded oil or grease. They do a fabulous job at reducing friction, when parts move very slowly with high contact pressure, for instance screws.
Even with oil or grease, don't use MoS2 on phosphated steel. The protection doesn't suffice, steel would corrode.
From what i read the MoS
2 is preferred to graphite in some applications. For instance, graphite does not work well in vacuum although it does work at slightly higher temperatures than MoS
2.
I am not sold on idea of graphite in oil or grease. Graphite, just as MoS
2 is a dry lubricant. Specifically in case of graphite, it can lump up when mixed with oil and cake up into semi solid aggregates. Locksmiths done tests and posted videos on youtube about lock lubes, which included graphite. Graphite beat all other lubes on the temperature performance, but graphite + oil was a mess.
https://www.youtube.com/watch?v=zZaPWGo8TbEThis is not a scientific study, but it gets the point across.
As far as additives in the bath are concerned, I'll try the teflon next. But next might not be any time soon.
I usually use vacuum chamber to suck oil into phosphate or black oxide layers. I like vacuum chamber results better than regular soaking. The phosphate bath additives i am playing with to see if i can actually embed protective particles into phosphate layer and either strengthen it or smooth it to reduce wear effects.