You use whatever you would use on horses for donkeys. I'm not sure the pour on ivermec would be the way to go. Better to use paste wormer for the donks.
I wouldn't use it on the donkeys. We have cattle and we never use on our horses what we do on the cows. Ask your vet. I've always heard it will cause bad skin issues on horses. Needless to say, tubed horse wormer is the best way to go if your not sure.