Hot girls give their number out to lots of guys. The "Wait 3 days" thing is old fashioned. If you wait more than 24 hours she's probably already booked 2-3 dates with other guys she met that weekend.
You need to get a girl to invest in you more.
The only reason why you should ask for a number is if logistics mean you cannot fuck her there and then.
Daygame blueprint: Open during the day, build a connection then get number and see what she's doing in the evening. If she's willing to meet you in a bar later that day, it's on. Alternatively, she may be free to go for a coffee with you straight away. In which case you should transition and move venues with her until you end up at your place the same afternoon for sex.
Nightgame blueprint: Always push for sex the same night you open her. Then you can choose whether you want to give her your number the morning after. I learned this the hard way, i had one-night stand girls calling me and bothering me for weeks (in one case MONTHS

) afterwards. It's easier to get same night lays if you open her after midnight, 2nd half of the night is when girls loosen up. If you open her early in the night between 9pm and midnight, build rapport with her, then blow her out to get her number, then text her something flirty right away so she remembers you, then open a few more sets. If nothing happens with your later sets, hit her up again to re-connect with her by phone (even better if you go and find her if she's still in the same club) then get her to go get food with you. Then keep transitioning venues until she's in your bed.
Don't waste time with head games or waiting a few days because you're pretending to play it cool. Strike while the iron is hot.