Dear Melissa, the procedure of coating depends on the specification of the product, if the product says it has to be done overnight in 4 Degrees then you got to follow that for proper use. what u can do for sterile conditions is wrap the the culture dish with paraffin so that even if the solution precipitates you will be sure its the sterile solution not from outside and after 24hrs in 4 degree you can even UV treat it for half an hour inside the hood before use.