This is a difficult question to answer since it depends on the matrix you are using. Generally for things like collagen, laminin, fibronectin, poly-L-lysine or something like that, we use 0.1 mg/ml using for example, 2 mls for a 35 mm cell culture dish. I use sterile water to reconstitute and dilute, then I add the volume to the dish and let it sit in the hood for longer than about 2 hours. Then I rinse with sterile water several times and let dry. I then store the dried dishes at room temp in the hood. For other matrices I recommend following the manufactures instructions. As far as autoclaving goes...generally matrices come sterile and all the buffers and media would also be sterile so there should be no need to autoclave.