Most of the time I use store bought frosting. I prefer the fluffy white. It IS fluffy, and works well with this technique. I've had great success adding food color to it as well. You need 2 tubs of this frosting for 24 cupcakes.
I use a mug to hold a gallon freezer ziploc bag. The freezer bags are a little thicker. Put the entire tub of frosting in the baggie.
Twist the top and snip about a half inch off the bottom of the bag.
Then in a circular motion pipe it on the cupcake, finishing in the center making a peak. I like the look of not going all the way to the edge of the cupcake.
I love adding these white sugar sprinkles. The sparkle just makes them extra special.
The result are cupcakes that look like I know something about cupcake decorating. LOL