Ideally, you need a thermometer to measure heat accurately and save you a lot of time. The soft ball stage is a good one to understand but unless you have mastered it through experience it can be hard to judge with the eyes. It’s more of a concept worth understanding than a practice that should be followed. The spoon or spatula that you use is important in creating the right texture of fudge when beating it. Alternatively, you can use a stand mixer with a paddle attachment to beat fudge with.