I'm new to royal icing, but I read somewhere that you shouldn't put it on a cake iced with butter cream because the moisture of it will dissolve the royal.
But in my cake books, I see a lot of pics of what appear to bc iced caked with royal icing on them also.
Was my initial info incorrect? Does anyone typically put royal on bc iced cake?

It can be done. Just don't put the cake in the fridge or in an air tight container.

I tried to do a royal icing stencil on a butter cream cake and it didn't work at all the royal icing melted. I do use royal icing for string work and some flowers with no problems but as for stenciling on butter cream I will stick with butter cream frosting.

I've done royal icing accents that were placed on a BC cake with no problem. The one time I had trouble was when I applied the accents and then refrigerated the cake. If you'll look at the bicycle birthday cake in my photos, you'll see how the RI started bleeding down the side of the cake because of the moisture.

It was a crusting butter cream and I will never try it again. It was my brothers wedding cake and I had to remove all the butter cream and frost the layer again. Royal works great on fondant but in my opinion not on butter cream. Butter cream roses or accents that have been air dried work fine.