I have a young boy that age! Aren't they the cutest, with their big heads?
To get them used to you faster, exchange those towels with shirts of yours that you don't mind being nibbled on - that way they'll smell you while they feel safe in their cage. I've done that with boy my boys.
But you're doing very good! Do they poke their heads out or run to the door if you're near or talk to them? Since they're licking on you and seem to have accepted you, it's time to try to give them playtime and to get them to bond even more to you.
For my younger rattys, I don't prefer the bed as playtime, just because there's a lot of places they can go and I can't grab them (and I have cats). So if you can, clear a table, put down a towel, and put lots of stuff on there for them to explore. My boys love it! Give them lots of special treats when they're out, so they start to think, "hey if we let mommy take us out, we get to explore AND get yum-yums!!"
You could even play with them. Gently tickle/rub/scritch the nape of their neck - that's how little boys play.
You can also gently grab them, lay them in the palm of your hand on their back, and tickle them! Rats actually laugh, even though we can't hear them! If they bounce around and run away then back, that means they want to play more!
Of course, if you pick them up and they squeak, that's normal. Also, while they're playing, talk to them. If they're a bit too nervous to play with you, just give them treats and keep your hands where they can smell you.
Be sure to update us!!
Edit/ As for the water bottle, I think it's just because they're young. They'll learn! I keep a tub of water in my boys cage, along with a water bottle. They use both, but the tub also gives them something to play in.