Keep it to a few simple texts then... and you can pre-define what they're going to say even. Put them in your phone's notepad and copy-paste them...
After you get the number:
"Hey! It's the guy who was hitting on you just now. Now you have my number as well

"
Next day you'll need a couple, then you transition to the call ASAP:
1) "Mornin good lookin."
If you can playful banter a few messages in between 1 and 2, that'd be great...
2) "So I'm thinking you need to tell me more about (something she talked about the first time you met her); Buy you a beer?" --- OR: "So I'm thinking about grabbing a drink after work one night this week - free to join me?"
If/when she agrees, call her up and work the logistics out on the phone.
Simple rule: If you're bad at texting, don't text.