Thanks for the plug Sandy!
Well I am sure there is more than one way to skin the baryta cat as it were...
The main hurdle to jump in coaxing pt/pd (or just about any other alt solution) onto/into the gelatin layer of fb paper is that of EVEN absorbtion.
Any fb paper will absorb the solutions...eventually, but probably unevenly. Unless you use a surfactant (like tween) the absorbtion will be less than ideal. I suspect that the success Annie is having is due just as much to the prolonged soaking of the paper as it is with any modification in the ph of the surface. Maybe a long soak removes something from the surface of the paper that hinders absorption. Maybe it changes the suface structure and/or opens "pores" in the coating allowing better penetration. I don't really know. I usually fix my paper then wash it for about an hour. I have found no real advantage to washing it longer nor have I found it to absorb the solutions better than if it had a very short wash. Annie's mileage however seems to vary from mine. Keep us informed about your progress Annie!
You may want to try adding a few drops of dilute Tween..say about a 10% solution to your coating mixture. You can even try Photoflo. It works...kinda. I am sure that by adding a surfactant you will find that the absorption will be much better.