Regarding Kitty litter ballast, I went to the supermarket this morning and bought a 10 pound bag of unscented, non-clumping and dust free kitty litter made of clay for $2.29. It was the smallest quantity they had, and is still well in excess of what I need.
I will take some photos when my smart phone charges up within the hour.
I agree that the kitty litter granules are too big, but my traditional O Gauge tubular 3 rail track is already way too big to be in scale so I think the appearance of the kitty litter as ballast works for my layout.
I have left the kitty litter ballast loose for now.
My concerns include will it cause rusty track pins and connections? A friend advised against it because kitty litter absorbs moisture.
Also, although it is dust free, will it get into the motor, wheels, and train mechanism and cause problems with the trains? I have not put any in between that rails, I only put it outside the outer rails.
I'm sure that the ballast made for model trains is much better than kitty litter ballast, especially for layouts with modern track in scale.
Arnold