How to get perfect sharped edges.

Hi all,
I always had some difficulties shaping perfect edges on my cakes.
I looked for tutorials on the Internet and found some one that were very helpful, but after all, not enough for me.
I followed a beautiful tutorial recommended here on CakesDecor’s forum. Please forgive me I didn’t save the post, just read it and I don’t remember the name of the lady who posted it. I made some changes that helped me a lot (I used styrofoam circles instead of plastic circles) and hope that could help someone else.
Have a nice weekend, my dear friends!

(First of all I have to say that I made an Italian meringue buttercream my way. This is the one I prefer to coat my cakes! The most boring part of the recipe is when you have to add small pieces of room temperature butter. It’s an endless process… So I thought to put the whole quantity of butter, in a pocket bag and squeeze it into the whipped mixture of egg whites and sugar: soooo easy and faster!)

I bought 2 styrofoam circles whose diameter is the same of the baking tin I usually use. I holed them exactly in their centre with a toothpick.
I inserted a long toothpick into one styrofoam circle to use as the base of my working station.
I put onto it a round baking paper sheet.

I checked the level of my cake.

I holed the center of my cake, checking the hole was perfectly done.

I positioned 2 layers of cake onto the styrofoam. The toothpick into the styrofoam was crossing the whole cake, locking it firmly. I topped with the other styrofoam circle, leveling.

I coated the cake with the buttercream.

With a large spatula, I smoothed out, following the edges of the styrofoam circles.

I removed the topper circle.

I filled with the buttercream, smoothing the top of the cake.

I chilled the cake, then put it up-side-down and carefully removed the bottom styrofoam circle.