I have to make about 40 brownies for a friend's party and need them all to be square and all the same size. What I really need is advice on a) best time to slice them eg hot? cold? still warm? as I never seem to do the neatest job and b) how do I measure them??? You'd think it would be so simple, and maybe I'm missing something here! They taste fine just really need to get them so they look aesthetically pleasing! Also what is the best size for one brownie? eg 4x4cm???? Any input much appreciated.