How do you all transition from txting to calling a woman? Do you txt awhile then just call out of the blue, do you tell her you're calling, how long do you want?

When you have the number, you call whenever you want. That's what the number is for.
Girls don't give out their numbers thinking "I can't wait til he texts me", they think "man I can't wait til he calls".
Their is no fact behind this, but I personally think most guys who texts girls(initially) are just afraid.
This is just my opinion.

I've txtd women a few times for a day or 2, then I go to call and they don't pick up. They txt back later on and say hey whats up, then I try to call again later and still don't pick up. I back off a bit after that but didn't know if there was a way to ease into the calling part sooner.

I sometimes call a girl like 5 minutes after I get the number and have left them. It's very unexpected, and you just play it off like it the new thing to do.
This actually started by a buddy of mine doing it by accident to a chick. He played it cool and since then, it's been a thing we do.

Don't get me wrong, some girls(maybe most of them), have just gotten so used to texting that you just go along with it.

But for me, I'm not a texting person, mainly because a lot of shit get's misinterpreted when texting.

Remember the one who survives is the one who is best able to adapt.

And at the end of the day just be yourself.