Yes it costs few bobs but if you rent the carpet cleaning machine like i used to do: (16eur a day in Midleton), bottle of Vanish Carpet cleaning liquid and you will manage to get your car super clean and fresh with just 2-3h work and 25 quid for chemicals and machine rent

Without carpet cleaning machine you will just rub the shaite more in, it may look cleaner but the smell comes back in a week or 2 and also the car gets more dirty sooner as the chemicals and shait isnt sucket out like the carpet cleaning machine does.