Our daughter just had her upper jaw brought out for the third time three weeks ago. We're hoping this will be the last time. lol
The hospital may give you some dry sodium stuff to put in water to rinse with. She still despite using that and brushing, has some dried blood up in the brace they have over her braces. It would drive me crazy if it was me, but luckily she doesn't care much.

All she cares about is getting the dratted thing off. lol
She doesn't have her jaw wired shut, but does still have some pain trying to open her mouth just wide enough to get a spoon in.
She is on liquids and soft foods right now. We've given her grits, soup, soft scrambled eggs, applesauce, baby food bananas. But, any fruit that can be put in the food processor would probably be good and a lot tastier than baby food. lol And, don't forget Ensure, smoothies, shakes and such.
Good luck on your surgery, too.
Kim