Disclaimer: This is not personal medical/dental advice, just my own understanding that I'm sharing.

Floss (or water pick) first, then mouthwash, then brush, then don't rinse.

Floss to open up the gums and knock loose anything stuck in between teeth.
Mouthwash to get rid of the solids and get a bit of fluoride in between teeth.
Brushing after mouthwash, because toothpaste typically has a much higher concentration of fluroide than mouthwash does.
And avoid rinsing after brushing so you don't wash away the residual fluoride from the toothpaste.