Contacting multiple potential supervisors at the same department? I am interested in topic X, and I would like to find a supervisor for that topic. At one particular uni, there are quite a few people interested in my topic, and I need to find out who might be a fit and whose interests are maybe not so aligned with mine.

Should I just message all of these people at the same department? Would it potentially reflect bad on me? I am also worried that in case two of these people are interested, I am facing a dilemma when applying. 

How should I proceed, how do these things usually work?
TL;DR: You should contact all of the possible supervisors at the same time and ask for a meeting or a call. And you should be completely open about the fact that you contacted multiple advisors.

Why:


If you contact one after another this gives (possibly) a bad impression for everyone.
I understand that you would like to prevent the dilemma of multiple advisors being interested but this dilemma will show up anyways once you have chosen a advisor and started the work. 
You do not want to be disrespectful but you are faced with a decision. Everyone should understand your dilemma and should appreciate your efforts to be as fair. 
You should be honest to yourself. While I do support your way of thinking you are causing this dilemma yourself because you want to have the choice.


I would think that the etiquette will differ greatly across the world, so I don't know how well it is received that you would like to have a choice/control here. However, I think it is totally understandable and a good advisor will also understand your intent and process.