There are times when the subject matter is so complex that the students fail to understand them. The standard practice is to ask their fellow students about the subject matter, or the professors who they think will have the most knowledge. They should ideally select an individual who can explain things to them in a simple way, and break down even the most complicated concepts for them. This should be the person that they should choose as their PhD guide.
The best guides are those who have spent many years working on a particular subject, and they have also chosen teaching as their mission in life. They are prepared to take the time and the effort to teach students in ways that would be easy for them to understand. The best guides have a passion for teaching, and they think that through their knowledge they can make a difference in life. That is why approaching them for assistance would benefit the student immensely in his work.
Dissertation projects are quite tough, and they can be confusing even for those who have quite a lot of knowledge in their chosen discipline. There are so many issues in the way that one can go about the project and even the experts are not sure how they can solve them.
It is in such cases that the students would be best served by taking the help of two or three guides who can advise them on different aspects of the case. For many students the guides are invariably two or three professors from their universities who have command over various matters of the subject. Thus, if one professor does not have all the answers, the students can always turn to another professor and get the help that he needs.