A couple of hundred lbs of weight directly over the rear axle or forward of the rear axle of a RWD vehicle will help quite bit with traction.
On the other hand, adding weight to the trunk of a FWD vehicle (like that Camry) will only worsen the weight distribution and will actually reduce the traction of the front drive wheels.
If you want better traction, ditch those so-called all-season tires for a few months and put a set of 4 winter tires on the car. Winter tires make an incredible difference in improving your ability to stop and take turns, as well as to get you going in the snow. They will even give you somewhat improved stopping ability on ice.