How Do You Comunicate When You Are Pissed?

Here I am at 40, raising my 14 yr old daughter. You might think that is the problem but it's not. Of course that is stress I am used to by now and wouldn't trade her in for anything different. 
The problem is my brother is temporarily living with us and driving us mad!  He will be here through Christmas.  He has taken over the living room as his bedroom (even though there is a bedroom for him). He doesn't pick up after himself.  He never does anything to help us out around here!! 
I cook, he eats.  But he can't seem to even clean up his own dishes let alone help with the rest of them. NO help financially either. He is 33 and is out of work because he has recently moved back to the US from Prague. (That is a whole other story)
Am I over-reacting?  I work all day, I am broke and tired. I would just like a little help. I have opened up MY HOME to him and now I feel as if he has invaded it and I don't know what to do.  I can't seem to talk to him about it.  I am afraid of.....????....I don't even know.  I am already walking around pissed off and he knows I am but  he says nothing...does nothing.  I don't want there to be a fight but I'm not sure I know how to avoid one at this point.  I am PISSED!  He needs to know but I get even more resentful wondering why I should have to say anything to him at all. I mean all I want is for him to give me some freakin' courtesy!   I want to write him a letter or something. Would that be to chicken-#*!# of a way to handle it?