I'm not a pro, but from what I have read in books and tested, the hardest part is yourself. You can influence pendulum if you are emotionally attached to a desired answer. That's why the practice is needed.

I use pendulum for two reasons - first, as a way to think about the issue and, second, to get rid of wrong ideas. You are forced to think out of the box and to look at it from different perspective. And that is how you get the solution. Pendulum just confirms your guess or not.

Of course, you have to believe that pendulum has access to your subconscious mind, Universal informational field or some other information storage that has the answers. If we skip the esoteric part, then pendulum can be tested. Find some hidden item or ask something simple that other person has written on paper and can be checked. That is a good way to practice.

You can use pendulum to ask what kind of book to read, where to search information or should you go to this doctor, or any other question that may help you. Pendulum does not give advice or make decisions. You are the one that should make a decision about doing those things. But Pendulum can give you the answer about what suits you and works for you better. And the question should be rephrased about those things.

Wrong: Is this a good thing?
Correct: Does this thing harmonize with me?
Then narrow: Does it harmonize for 100%, 80% or 50%?

Pendulum (Subconscious Mind, Universe or whatever that gives the answers) does not understand what is good or bad in your opinion. So, you have to ask what is in harmony with you.

Here is another thing on how I understand things.

As a person you have some thoughts and belief system that was made up with the help of environment you were living in. This belief system is in conflict with your Soul. As a result you are upset about something or somebody, that makes some stress, stress creates some blocks in your physical body. More conflicts, more stress and pain for your body. Then your body gives up and you get the result - disease.

Some books says that unconditional love and forgiveness may help. Then you need to find the technique you are ready to work with.

The idea on how one prayer may sound like.

Forgive the disease that it came to you. Forgive yourself, that you accepted it and let it in your body. Ask for forgiveness for your body that you did not know how to release it from it. And now you are free. You love everybody. Even the disease, because you learned something from it.

P.S.
Another idea. If the disease has affected only legs, then maybe it symbolizes something about going forward, moving on or not wanting to go somewhere. Legs symbolizes a movement and you may have an inner conflict with it. Like you do not want to upset somebody and do not know how to do it. So, your body helps you with it and you have physical problems with movement. As a result you do not go where you did not want to go and it looks as a good excuse.