How to teach my daughter express herself

My seven-year-old daughter has a hard time expressing her opinion and opening up. Can you give me a few ideas to help her talk more freely with me? I am homeschooling now, and I can put it on her schedule. How do I explain that this is part of her school? How do I call this? A speaking class with Mom?
Her dad and her older sister, who is nine, are very strongly opinionated, and they never finish their sentences, so the seven-year-old and I become their listeners.
How do I correct my nine-year-old from taking too long to express her point of view? She loves talking and not much listening. She is showing characteristics of being oppositional and argues with me when I try to correct her. I know I need to pre-teach.
I can not ask my husband to help because he doesn't see himself as doing anything wrong.
Thank you very much.