
Dont laugh, I have detailed cars for over 20 years.
Get a 5 gal bucket use a 1 cup of tide and about 1 cup of 409 to 3 gal of hot HOT water.
Spray 409 on bad spots in the carpets or seats. Dont let the 409 sit longer than 5 min. It has small traces of bleach.
Use a stiff brush to scrub the carpet and seats.
Get a wet dry vac to suck up the water and dirt.
Get a hand towel
This will help you after you remove the seats and carpet.
1 Spray 409 on spots.
2 Use brush and handtowel to transfer soap in bucket to wet down the carpet and seats. make sure they are wet enough to scrub.
3 Scrub the carpets and seats.
4 Wet dry vac the seats. look to see if your seats have a nap (one way the fabric will stick up and show off the rich darker look) vac so this shows when it drys there is almost no soap/water left.
5 Next use a hose to wash all soap out. The vac out as above and watch the nap of the carpet.
6 Protect all elec items. Remove or cover sensors, computers etc.. Next use soap mix to soften up the beer and crap of floor boards. Scrub with brush and vac up water. Towel from soap mix can clean up dash console, doors etc... scrub panels as needed. Dry towel and your done.
As for your headliner best to use osium sold in most part stores. Cleaning a headliner MAKES MOST FALL APART. However some stains can be removed by lac/thinner on a WHITE rag. White will pull other colors to it. Rub soft dont push in as you rub or you'll have a indentation in the headliner.
happy cleaning.