I am doing one of those Rainbow Sprinkle Cakes and using the NON-PAREILS.

Is is better to attach them to buttercream, or cover the cake in fondant and brush it with piping gel?

What do you find works best and looks good.

I have only stuck them to buttercream.  Be prepared for a big mess!  There are tutorials out there with great suggestions on how to keep the mess to a minimum.  I'd suggest googling it.

AI'm waiting on the responses you get too :)

AJust had a chat with the owner / cake decorator of a cake decorating supply shop I frequent. She insists buttercream is best as ganache does have a firmer slightly oily finish even when using when it's quite soft. She says this makes it more difficult for the 100's & 1000's ( non pareils ) to stick & stay put. She says she has made plenty and only ever now uses buttercream. Somewhat of a challenge for me with NO DAIRY allowed but I imagine it will all pan out. :-)f

Perfect.  Thank you !!