Guys, can you explain to me what milking the intro means? is it when you make your introduction/opener longer than the usual? and what is it's difference from regular open?

Milking the opener means you're putting too much effort in it. According to Style, each opener needs to have four goals: it has to be non-threatening, stirs up curiosity, springboards for a follow up conversation, and serves as a vehicle to display your personality. The 3rd and 4th points are very important. You need to change the subject, and you need to display a good personality that they start to ask YOU questions.

If you milk the opener too long, then you appear to be a survey taker who has no interest in the set as individuals. You want to convey to them you're a social guy who likes to talk to people, especially strangers, and that you do it all the time.