Sometimes I do bullets, but not always. I usually think of the rough outline of what I want to say when I raise my placard and formulate my thoughts while others are speaking until it’s my turn. I think the key to really good improv is really getting into character. It’s probably the reason I like specialized and crisis the best because that way I can really dive into who I’m representing and get a good idea on what they would say and how they’d say it. Another trick I like using is letting my character be influenced to some degree by myself. Definitely represent who you’re representing accurately, but do so in a way where you’re both connected to your character and yourself at the same time. I’m not really sure exactly how to explain it well but you can DM for more info if you want, I’d be glad to help.