Mine were very rusty, too, from sitting 10 years. If your brother takes off the wiper arm and the escutcheon beneath it, he will see the spindle and the part in which it turns. He can then use penetrating oil there, and gently turn the spindle under the dash, after disconnecting the linkage there. He should be able to work it loose this way. Once it turns freely, oil it with engine oil and reassemble. I suspect regular oiling of these parts is something generally overlooked.
Someone else may have a better idea.
Joe
