I have found that at least on asphalt, if you use tires from the same family (yellow-green-blue/white-grey-black/pink-magenta-purple), the balance remains best when you apply the same coat of traction compound front and rear. I always put on a full coat front and rear. I found that if I use a less than full coat on the front to get my car balanced, this will only work for three minutes. After that, the rear will get unsettled, because both the fronts and rears will run without traction compound.
This is with a 10th scale pancar, but it should be the same for 12th scale.