I'm going to flirt with two girls at the same time
Do you feel the same way to both of them?
I have lustful feelings for one of them, I feel great respect towards the other girl.
You should be honest with the people you are interested in. If nobody is committed it is ok to flirt with both.
If I'm honest they may hate me since they will know I have a different feeling for them. I would rather separate my feelings and focus on the task at their expense. I have been on the receiving end of that before myself.
Just because it has happened to you does not make it right to do it to others. Be the bigger person and be honest with them both or don't flirt at all.