What year, make, model, vehicle are you going to do this to ?
Are the seats cloth or leather?
How dirty are the carpets ?
What make Extractor do you have? Are you very good with it ?
I use a Meguiars APC that is no longer available except I think in 55-gallon drums if that...
The next best APC is probably this one -
Meguiars Detailer D101 All Purpose Cleaner
You can mix this 10:1 for light work and 4:1 for heavier soiled cleaning...
I would vacuum really, really, good, using a stiff brush to move the fibers around to get as much dirt out of the bottom of the carpeting as possible..
Then, spray the mixed cleaner on the carpet, adding extra to the really dirty places. Try to use as Little soap as possible to get the level of cleaning you need... Don`t go crazy here - remember, you still have to rinse it all out and extract it...
Then, scrub it in with a TuffShine Tire Brush --
TUF SHINE Tire Brush
Now, when you brush carpeting and floor mats, you have to be careful to
- Not - change the pile, so dont go crazy hard here, start off in 1 direction, then another, checking to make sure you dont change the way the carpet bloom looked before you started..
Then, using the Extractor with only clean heated water, key the tool over the areas pressing down firmly to get the water as deep as possible.
How fast you go or how slow you go injects less water or more water, so
think about this before you start..
Do 1 extractor width tool line at a time, going back and forth..
If it looks like you have all the soap out, then just keep going over the rinsed areas
- a lot - with the extractor tool to pull up as much moist, dirty water as possible... The more you extract, the cleaner the carpets will be.. The cleaner the carpets are, the Cleaner the vehicle will smell...
If you dont get all the dirty soapy water out, the carpets may dry either hard, and not look great, or may dry and get very dirty very quickly, because the soap left in the fibers will attract dirt and hold on to it..
When you are done with all the Interior carpeting, carpeted mats and Trunk carpeting, you should have a huge amount of dark brown water in the Recovery Tank of your extractor...
I always get 4+ gallons of dark brown, dirty water in my Extractor recovery tank, and it still amazes me that this much dirt came out of such a small area..
If the seats you referred to are Cloth, then it`s the same process I outlined above..
Just be more careful - some cloth is not very strong if its old and might loosen up or do weird stuff..
Be even more careful how much soap you use, because you have to rinse it all out and extract it all out, so you dont want to get it stuck in the foam too deep..
Some foams - especially German Seat Foams - will soak up water and NOT want to let you extract it all out Easily... So be careful if its a German car..
Good Luck !
Dan F