I am in the process of building a flagstone walkway for a customer. Flagstone isnt very popular around here at least for sidewalks its mostly used for walls. What is the best product to use in the joints? Its blue gray weathered flagstone with several different colors in it. I have heard gator dust, crushed granite, topsoil and grow moss, and stone. I read some bad reviews about gator dust staining the flagstone and the homeowner said pick any color stone you want to use in between she doesnt care as long as it looks good. I have had a hard time finding crushed granite all the local suppliers dont seem to have it. I figured I would need a 1/2" stone at most so it can be packed tightly. Maybe 1/2" river rock?