Should you just work with pastel pencils?

Initially, when you’re starting out with this medium, it’s better to work with nothing but the pencils until you familiarize yourself with them. And once when you start to grow in confidence, then you branch off to other sections such as fixatives, which deal primarily with preservation, along with blending stump. 

Tools such as a blending stump or even a tortillon can be a fantastic way of getting more even gradients in your artwork while employing newer techniques and sketching methods.