I have an older yellow lab and black interior. Between his fur and slobbery jowls, keeping my 4R clean was an up hill battle. I found a low cost solution, that while its not the most visually appealing, it works really well.
1. Take a black queen size bead sheet (unfitted) and draped it over the rear seat so half the sheet is over the front of the seat and half falls down the rear of the seat.
2. Marked out where the head rests are with chalk.
3. Using the head rests marks as a guide cut holes/slits in the sheet for the head rests to go through. Test fit the sheet over the seat and head rests.
4. Sew around the holes/slits to keep them from further ripping.
5. Place a black pillow case over each head rest.
6. Drape the sheet over the rear seat with the pillow case covered head rests going through the holes/slits.
7. Tuck edges of the sheet into the crevices around the back seat, and cover the cargo area floor with a matt of your choosing (WeatherTech).
This solution is cheap, easy to set up, easy to remove, and easy to wash. Cleaning the slobber marks out of the seat fabric was just as big of a pain as getting all his fur out of the fabric, and this solution take care of both. I will post a picture when I get home...if I remember.