The best way to clean your carpet and upholstery, if you don't have the big tools, like a deep cleaner extractor, is to use this spray shampoo like in the OP, and brush it in to agitate everything. Once that is done, vacuum up everything that has come out.
To get smells out, try using an aerosol odor bomb that locks on and circulates through the car's HVAC system. Many of the smells inside a car come from moisture and mildew trapped inside the ventilation system, especially in AC equipped cars that are run with the AC on for short trips. This builds up lots of moisture in the system and causes mildew and mold. This is also a good idea for a vehicle that has been smoked in.
The odor bomb takes a few minutes to fully release and needs to be undisturbed for a couple hours. They typically run around $8-15 per can.
The interior shampoo will help with smells, since obviously the carpet and seats will hold odors. The best way to do this is pull your seats out of the car and do the entire carpet and do the seats while they are out of the car so you can get down the sides of the seats, and clean absolutely everything.
The vinegar trick works too, but many people find the smell of vinegar just as offensive as the offending odor to be removed, so sometimes it isn't the best plan of action.
One more odor eliminating trick is a product you can buy that you spray into your car's fresh air intake vent. Let this circulate through the system, and it gets rid of odors in a similar fashion to the odor bomb.
If all this still fails, you'll need to steam clean the upholstery and carpet. While you have everything out, peek under your carpets and spare wheel well and make sure it isn't wet and mildewy. You can also spray down your seats and carpet with a degreaser and pressure wash them. It's totally safe to pressure wash your seats, you will not hurt them or the foam. It all dries out. However, be forewarned, it will take a long time for the seats and carpet to fully dry out, so make sure you've got another ride for atleast a day or two. Last time I pressured washed a set of seats, they had to sit inside the shop for the weekend before they were dry enough to put back in.
I work as a detailer, and I've come across my share of smelly vehicles, from smokers to cat urine.
Back to the original carpet cleaning topic, make sure you use a nice coarse bristled brush to agitate the carpet. If you have stuff like gum or other things stuck in your carpet, spray a degreaser like Spray Nine or Simple Green green on it and brush the crap out of it and vacuum it up.
