No, it’s not the best approach, either for the missionaries or for you.
It’s not the best approach for them because you look rude. What do you think that tells them about the Catholic faith? We’ll tell you: It tells them the Catholic faith makes bad Christians. Now we know you’re not a bad Christian, but all they know of you is the door being slammed in their faces.
Your technique is also bad for you because it gives you an excuse not to learn more about your religion. If you made a resolution to talk with missionaries in the future, you’d find yourself doing a little homework. It doesn’t matter how long you’ve been away from school–no one is too old to learn.
Besides, learning about our faith is both easy and fun. Many Catholics kick themselves for having put off studying for too many years. Now, after just a little time with the books, they have a better appreciation for their faith and find the Mass, the Bible, and their devotions mean much more to them. Don’t hide behind a door. Learn your faith–and proclaim it!