Ok...I checked the Adox page....it looks like they do have a gelatin coating that they call "undercoat" - I guess thinking once you put your own emulsion on, it will become the undercoat or a barrier before the baryta coating. In any case, perhaps if brushing is too harsh - have you considered rod coating. Hardening the gelatin might be an option to try out.
One way to make the coating more receptive might be to wet it beforehand, perhaps with some T-20 added and dry it just enough to keep some moisture around. Kind of like wetting a sponge and squeezing the excess out. Then apply the sensitizer. That might help with the uneven absorption and blotchiness.
Would gum bichromate be more suited for this paper, I wonder.
Just some thoughts....
:Niranjan.