I don't think there is a lot you can do. I don't think I've ever saved a shrimp that was on it's back twitching. By the time it's at that point, at least in my experience, it's over and just a matter of time. For a few people that knew it was a molting issue, they're been able to remove the molt for the shrimp, but in the cases of it being something else, there isn't much people have been able to do.
20g platy, , 2 x 10g shrimp, 3 x 20g shrimp, 7.5g shrimp and 1 great dane/mastiff puppy.
Sump Pimp #2
My Tanks and my shrimps