What kind of vacuum gamit mo? I would strongly suggest you use a 1300Watt up vacuum cleaner... Vacuum it using an upholstery brush attachment... di pwde flat attachment or hose lang, di aakyat yung alikabok at dumi...

better if you can use a separate brush (a nice, stiff horsehair shoe brush would work) then brush and vacuum thoroughly.

You can also spray some dust mite killing spray (meron sa ACE HARDWARE) to get rid of the dust mites in your seats...

Best if you can shampoo the seats, go get yourself a couple of cans of turtle wax upholstery cleaner and tons of towels/sponges to do the job