although there are around 20 muscles in your forearm, all you need is one bar(and plates for advanced trainers). you can do 4 exercises to target all the forearm muscles by performing the 4 actions of the wrist, meaning abduction, adduction, flexion, and extension. you do not need plates for adduction and abduction but you might need them for flexion and extension. the good thing about these exercises is that safety comes first, you do not need to go through an exaggerated range of motion to perform the exercise. although the full range of motion is good for muscle, when it comes to fragile body parts like the wrist, it is better to find exercises that do not demand it. these exercises are easy to progressively overload and easy to perform. in the end, as a bonus, I advise you to involve some type of hammer curl inside your programme to target brachialis and brachioradialis. the difference between these two muscles and the other 20 is that these two muscles do not affect the wrist movement but affect the elbow, in other words, all they do is elbow flexion and do not affect wrist abduction, adduction, flexion, and extension.