Hey guys, I followed this thread and did it to my carpet this is how it was:

The guy that owned this car lived in a dirt road and had no floor mats on the car so you get an idea. By the way this picture is after a long vacuum and some carpet cleaner that didn't help.
Another pic

You can tell how dirty it was.
Look close on this pic there is a stain where the passenger puts his or her feet down. I think that was either dog poop or cat poop, still smelled a little bit but it was hard as a rock
So after taking the carpet out I took it to the car wash and pressure washed it with soap. It helped a lot, but it still was dirty so I let it soak overnight with some armor all car wash and simple green and water. When I took it out I threw it in the washer with regular washer soap. Even though it didn't help much it was smelling great. But since it was still dirty I borrowed a professional vacuum, one that sprays soap and then sucks it up. After a lot of scrubbing and vacuuming I took it to the car wash again but this time I didn't use soap. I let it dry overnight and next day I noticed there was still sand on it so I dry vacuumed it for a while with some scrubbing (dry). Then I painted it with the carpet spray paint and this is what it looks like now

Not only it looks great but it smells great. I took the time to wipe and clean every piece I had to take out and know my car smells great.
This is the passenger side (no dog poop stain! yes!!!)
And this is the rear seats area
By the way this pictures were taken after a month and a half of doing it and I still haven't vacuumed it so it's not crisp clean but you get the idea. Thanks for reading