To add a degree of "wwww" to the discussion, it is often said in medical circles that chest compressions aren't being correctly done if no ribs are broken in the process - as an indication of the pressure required to do 2". It feels horrible, but when you have a beating heart at the end, then you don't mind so much, ribs heal.
It's a fact that any compressions are better than none, and I have to agree with the above comment re Vinnie Jones - it's about the best infomercial out there.
This following product comes highly recommended, and I think should be part of any first aid kit, certainly in cars.
http://www.laerdal.com/gb/doc/113/Laerdal-Pocket-Mask
It allows the user to give mouth-to-mouth breaths without any lip contact, indeed there is a built in filter, and the mask itself can aid getting a good seal, although it is perhaps easier with a second person helping.
Being an anaesthetist, I feel this is one area I have some experience in.
Cheers,
Adam
P.s. Feel free to ask any questions of me, public or private.