I'm a newbie!
Saw that you guys are talking about WBH buttercreams. I tried both the House and Kaye's italian meringue buttercream. I don't quite like the House due to the shortening - i'm a butter person. But I love the italian meringue buttercream. For me, it's slightly on the soft side but still ok to do roses. Of course, with warm hands, you gotta work quickly. But for other simpler flowers and borders, it works very well and smooth not to mention tastes great! I think you'd have to make sure that the egg white and sugar mass is as cool as possible and to have the butter chilled, as in the receipe. Because if the egg white/sugar mass is still a bit warm and the butter only slightly chilled or room temp, then i think the buttercream will come out very soft. I'd put it in the fridge and check on it by stirring it with a palette knife and see whether the consistency is to your liking. It will definitely firm up in the fridge.
I've kept this for over a week in the fridge. It looks broken at first but take it out and let it soften at room temp. Beat or just hand stir - if small amount and it's ready for piping. Anyway, that's my experience with Kaye's buttercream. Hope that helps.
Btw, also tried coloring this and man, does it take in a lot of colouring. I found that candy colours works well and wilton pastes somehow separate?? Did anyone also experience this with wilton pastes?