AHow to attach satin ribbon to buttercream cake without it becoming grease stained,

You can cut a piece of wax paper the size of the ribbon and use it as a backing so the ribbon does not touch the cake.  You can use ribbon that is not cloth more of an acetate and for me it has not soaked the grease.  Others on other thread go ahead and brush shortening on the back of the ribbon but it will change the color.