I've seen articles and dentist recommendations both ways. But the consensus seems to lean towards after. You want the fluoride to sit on the teeth and get absorbed as much as possible. This should provide a larger benefit than the damage of brushing when your teeth are, and not brushing means just leaving that gunk on the teeth even longer to mess them up more. But yeah, I guess you aren't supposed to wash your mouth out after brushing or mouthwash, and avoid eating/drinking for about 30 minutes. Just try and spit it out as best you can, that's how I've done it for years, takes a little getting used to but isn't something I notice anymore.