Try this for fantastic results:
1. Pre clean with a sea sponge, getting the fabric nice and damp (which also allows the next pre spray good distribution).
2. Pre spray with Alltec's Traffic lane de-greaser (not traffic lane cleaner) or Prochem's Fabric Restorer.
3. Scrub
4. Wipe off with terry towelling (gets loads of soil off, and its nice to show the custy

)
5. Rinse & Extract with Ultimate Master or similar
6. Towel off removing excess moisture/tram lines etc
7. Turbo dry for maximum effect and custy satisfaction
Obviously I dont know what your charging but if its bottom end then the above wont be very cost effective.
For overspray this comes with experience I guess, you can use your hand to cup the tool and catch it in these circumstances.