please remove the wiper scuttle panel and the wiper motor including arms, apply a generous coating of body cavity wax to the area and install back.
mazda 808/rx3/929/rx4/rx5 wiper motor is in a vinyl or thick plastic bag originally to protect it from rusting. To install the bag you would need to disassemble the motor from its first linkage. Use a solder iron to make the hole around the motor arm, the hot iron makes a hole that will not tear up later on.
You will also need to make the tail lamp rubber gaskets which prevent water from seeping into the boot area and start rusting. Buy some thin closed cell foam sheet to make this and use a generous coating of body cavity wax first to make a good seal.