Hello Jamie,
I was a car Valet for about 18 months and we cleaned car interiors successfully with a Puzzi, the CDT902 is significantly more powerful so it is more than capable of achieving top results......
The first thing is to make sure you cover all your interior where electrics are present or try to avoid over spraying.
Clean on a nice warm day and if you can't get your hands on an air mover, you'll need the car doors open to aid in the drying process. If any of the seating can be removed from the car, do just that, it'll make your life easier.
I would simply prespray and genty agitate with an upholstery brush and leave to dwell for 10-15 minutes before rinsing.
Ensure the windows are left slightly open for a good couple of days to let the condensation escape.
That's how we used to do it and the job was always a good un!