How can I get my co-workers to stop relying on me for everything and interrupting my work to help them?

I was recently promoted to a coordinator position, and I do not have much management experience. There are a couple of people on my team who ask me questions ALL day long. Of course I am happy to provide guidance, but it is almost as if they need my permission to do anything because they don't want to make a decision. In addition to the questions, it is the timing of the questions...my coworkers will rudely interrupt me while I am in the middle of a conversation, or they will come find me while I am on my lunch break so they can get an immediate answer. I have tried extremely hard to be patient, to direct them to the place where they can find an answer, and to stress to them that I have my own work to do and may not be able to ist them right away. It has not worked, and now I feel that I am being taken advantage of. I am afraid that soon something will get on my last nerve, and I will say something I regret. How can I tell them to leave me alone, do their own work, and wait until it is convenient for me to help them in a professional courteous way?