Reading out loud is a great way to warm up, definitely keep doing it. You might even want to start reading out loud every morning for example, if it works for you then build on it. It doesn't have anything to do with performing, you're warming up to get into the flow. Also, a good tip might be: while you're reading out loud, often remember yourself that you are able to speak very good (assuming you're close to perfectly fluent when you do so). It helps in your confidence. For most people who stutter it's important to create those positive experiences to convince themselves they ARE able to speak fluent. Try it out and I hope it helps.