For making churros, it's best to use a star-shaped piping tip with a wide opening, ideally at least 1/2 to 1 inch in diameter. This helps create the traditional ridged texture on the outside of the churros, which not only makes them look authentic but also helps them bake evenly, resulting in that crispy exterior and soft inside. If you don’t have a star tip, you can still use a round tip of similar size, but the texture might not have the same ridges. The wide tip size is key to getting churros that are thick enough to hold their shape during baking.