Hi everyone

Newbie here, I'm hoping someone could help me!

I have a cake order for Decemebr which requires me to use Royal Icing to cover an 8" cake. I cover the cake with a thin layer of buttercream, leave it to set and then place the RI on top.

I can't, for the life of me, get all the bumps out to achieve a nice, smooth finish. I've tried everything! I make sure the buttercream is as smooth as I can get it, but I'm still left with bumps which I can't get rid of.

Is a cake polisher really worth buying? Will it solve my problems?

Thanks xx

Several people on You Tube show you how to get perfectly smooth buttercream:
https://www.google.com/search?q=you+tube+smooth+buttercream&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-USfficial&client=firefox-a
Then make sure you sift the powdered sugar through a fine sieve when you make the royal.

OK........but I can't for the life of me fathom putting royal over buttercream............

Royal is usually reserved for a smooth covering over the marzipan on a fruit cake. It's just not used over buttercream--for the reason that you've already discovered--the buttercream moves around when you try to smooth the royal over it.

Grease breaks down royal icing. Buttercream is made of grease--either butter or white vegetable fat. All buttercreams come to room temp on a cake and when that happens, the fats come to the surface. Marzipan has a lot of nut oil in it (fat), but it's a pretty solid substrate.

The better option for covering the buttercream is rolled fondant. Your buttercream still needs to be pretty smooth, but the fondant will work. I don't think the royal will work.

JMHO
Rae