How do I avoid angry responses doing cold approaches?

I've been working on overcoming approach anxiety. I'm slowly becoming more confident, however I noticed I don't know how to respond well to flirtation. For instance I'll say "it's cold outside today" and the girl will say "nope" and I'll respond "you don't get cold?" And she'll say "nope". I was going to make small talk with a receptionist and when she postponed our talk to help another person, while I'm looking for the right words to say to flirt and say something funny I instead shrug and sound irritated for having to wait. What's the solution? The more I practice the more I realize what I'm doing wrong which I'm grateful for because I know I have a long road to go in raising my SMV, but this is where you start.