I usually practice with an all shortening buttercream and disposable decorating bags. It is cheaper than using butter, and as I finish one design I just scrape it up from the wax paper and put it back in the bag. I never use this for anything else. The american buttercream that I use on my cakes is either half and half or all butter. I need to practice more with royal icing, but I have yet to need to use it for any of the design that I have made. I tend to make specialty cakes or wedding cakes.