how do i put ribbon on the bottom of each tier of a wedding cake, without any "greasy buttery" spots soaking through?  and what to i hold it together in the back with.?  thanks so much!

I would like to know also.

I learned that if you spray PAM on the ribbon and let it soak through then you won't get spots because it's already greased. Makes the ribbon a little darker so you might have to try a lighter shade. I always pin my ribbon in the back with the pearl pins. I hope this helps :)

I have seen putting a piece of waxed paper or clear contact paper behind it, but it still gets splotchy, if you are not careful. I won't do it anymore because it is not a good representation of my work. And the ribbon can get a LOT darker. You can just soak a ribbon to see how dark it will get. If a client insists on ribbon, I will insist on a fondant covered cake. And If it has to be buttercream cake, then it has to be a fondant ribbon. I will not compromise on this.

Melt down some fondant with a little boiled water , and apply sparingly ,it doesn't leave grease marks. 

You can also slightly dampen the fondant with a clean paintbrush and some boiled water and it will stick. 

You can also attach with double sided tape . 

Or you can wet the ribbon in boiled water and ring out the moisture by running it through your fingers , it will also stick to the fondant. 

I am currently working with a ribbon supplier to see if we can get some ribbon that will not soak up the oil.  I would love to see something on the market that we can use without worry.  For now I also only use fondant on buttercream.