Whether a seasoned baker or new to the game, using a pastry bag is something that can be fun but also difficult. With some practice and following some general rules-of-thumb, hopefully you'll be piping like a pro in no time!
DO pick the right size bag. Pastry bags come in a variety of sizes. If you fill a large bag, it will be hard to squeeze and quickly move. For cupcakes, choose a small to medium size bag and for something like a cake, pick one that’s a little larger. You can always refill the bag so make sure to keep that in mind. It may seem easy to fill it at once but it might backfire!