Depends on what you want to do. If you are happy with <=20 outputs, you can use the uavcan.equipment.esc.RawCommand that is built in. You will probably have to change the definition of the actuator_output message and tweak the UAVCAN code a bit to make sure it grabs all of the commands. I can't remember exactly what all I had to do to get it working. I am running all custom code, so I'm not sure how any of this interfaces with built in features such as mixers and the like.
If you need more than that, you may wan to look into using the uavcan.equipment.actuator message. I just duplicated whatever was being done to send the esc message and modified it to fit the definition of the actuator message.