I've been taking Robinul for about a week now and it has been helping me with my palmo/plantar HH. I can't say I'm completely dry 100% of the time, but it's a vast improvement. I've only been taking the 1mg doses 3 times a day, so I haven't experienced too much dry mouth aside from the first two days I took it which were pretty bad (but worth it).
Sorry to hear the dry throat is bugging ya. How long have you been on it?