Rocko9999 -
Tks for your reply and the pics! Wow ! You really had it all apart ! Great job !
I`m glad I did not have to go to that length on that M5...
The only difference I can think of is that I used a really good Steamer the VX5000, and for sure, steam will always help loosen to remove most things faster and easier, in my experiences..
My Extractor is the Mytee HP60 Spyder which has a lot of water lift, and that helped me get my Meguiars APC+ and Steam deep into any cloth/carpet areas (and then inject really hot rinse water, and extract it all out..
The more you inject into those areas, the
even more you have to extract, if you want to get all that stuff out at the very bottom of the area..
Since you will never be able to extract all the moisture, I had to use 5 small Air King Blower Fans, to help dry out that moisture from the floors of all seats, and one in the trunk to help dry that carpet there...
I needed it to dry fast so I could see if I needed to do any rework...
It looks like the headliner on that vehicle is the type that is glued onto a hard piece of foam, is that what you have? That might be easier to clean, but you still have to be very careful to not disturb the glue that is holding the headliner to the hard foam...Perhaps that entire piece can come out ???
Extracting water from foam ? Yes, it can be done, but you need a really big, strong extractor, and it will take hours and hours... Foam is like lake bottom clay... It will take awhile for it to absorb water, but when it does, it will absolutely absorb a lot of water and will really not want to let it go... I did that seat foam extract on another BMW that had sat out all night in Seattle with the windows down and well, you can imagine, how that turned out...
I was able to get perhaps 95% of all the water out of all those foam seats with my HP60, , extracting from the bottoms, but it was very laborious and took hours and hours... Blowing a lot of air across those foam seats after extracting also helped get them drier...
You have made great progress !!! Great Job !!!
That rubber piece on the back of the upper back seat - I would use my process the same there, spray cleaner, steam it in carefully, wipe it down carefully, looking to see again, what is coming off, and what color it is, etc...
Door panels - I never had to undo those, thank goodness..
Something I just thought of -- The only
other cleaners I used were the old Einszett -1-Z Deep Plastic Cleaner, which is now called Nextzett, from Germany...But you cannot use this particular cleaner on any of the clear dash gauge clear plastic lenses, Nav Screens etc.. Instead for those delicate things In my experiences, I have had great results with Nextzett Cockpit Premium... The cleaners from Europe - Great Britain, and Germany, have always worked so much better than most stuff here, in my experiences..
Be sure to find the inside Cabin filter usually behind the glove box, and change that one out too, wherever it is...
You are almost there ! Every square inch !

Good luck !!
Dan F