Something I saw somewhere that looked like a good idea was to take a length of garden hose, make some holes along it through one side, and screw it into the wall where your door would contact the wall. So you'd have a rubber strip along the wall made out of the garden hose, and the screws would be 'inside' the hose so they couldn't touch the car wall. You'd make it long enough that both front and rear doors would contact it rather than the wall.
Sounds a little white-trash like, but it is just your garage after all.