Sometimes I alter the pitch and tone of what I am saying ever so slightly. Or pretend I am in a very VERY good mood. (Bonus: sometimes I actually get in a better mood by doing just that). I am all too familiar with the "ah... let me think..." reply before I answer a question I already know the answer to, so i can relate. Common trick I often use to buy time so I can scan through my brain for a synonym or a way to restructure the sentence entirely.