I’m new to using heads. Just acquired a 240 SD with a Sanipottie that has a pump out plate on the deck. Instructions say to never add deodorant to holding tank through toilet bowl. It is technically a porta potty, but it’s fastened in place so I can’t tip on its front to fill holding tank. Do I pour deodorant through pump out plate at the deck? When is it best to add deodorant? After each pump out when holding tank is empty, or do I need to first pump/transfer a little water through bowl and into holding tank?