Yes, I have done coating on the emulsion side and my experience was that the process was finicky, inconsistent, and the image was difficult to clear. I believe that in the silver emulsion contains some kind of resin that is resistant to additional coating. Craig Koshyk who is an experienced practitoner of this type of coating gave some information here...
My paper chase still continues..... After a polite 'kiss off' from both Bergger and Kodak I am now pursuing a recipe for the ideal Pt/Pd custom handmade paper... That way hopefully I can find the perfect pulp (a pinch of gampi for lustre!) with the perfect size and the perfect paper finish... I really like the idea of having a paper with 4 deckled edges that is dimensioned to my 7x11 negatives... You can actually have paper made to order by master papermakers for about twice the cost of 'off the rack' papers... personally, I am planning to 'hot press' my paper with metal plates through an old intaglio press.
If anyone has any ideas for the 'Perfect Platinum Paper' recipe please post!!