Advanced tongue cancer- what mouthwash helps numb the pain?

Hello,

my dad has advanced tongue cancer (in lympnodes and lungs) and he was told there are mouthwashes that he can have before he eats and after to help numb his throat so he can eat. We didn't manage to get the name before the appointment ended and all the ones online we see are for chemo mouth ulcers. Has anybody else used any numbing mouth washes to help eat when there's cancer in the mouth?

Thanks in advance !