a. I was using it for print-out Pd, at times when the RH was too low for a decent print-out and/or neutral(ish) hue. It's a humectant (and inert - regarding the reactions that occur during exposure and/or development), therefore helps very much in retaining moisture in paper. (I was adding 2-4 drops per ml of coating solution...)
b. I know it can also be used diluted 1:1 (with developer) for brush development of pure Pt prints...
What is your actual problem - that you think glycerin may solve? If it's poor absorption, then I'd suggest a non-ionic surfactant like Tween...