I am a newbie to cake decorating and this works beautifully.
I suppose you could even use standard parchment paper that comes on a roll too. I just have always used a triangle because it is what I have on hand.
I use a bench scraper and IMBC. It's just a matter of practice and a light touch, as FSSF said. Frost your top, then your sides. Scrape your sides, Smooth your edges to the center. Very light touch!, Then keep smoothing toward the center. You'll get smaller and smaller lines.