Hi
I have been using AR formula with the Tommee Tippee closer to nature bottles with a number two teat. To start off with our bottles used to get blocked, as when you first shake the bottle its like a thick shake, but now i pre shake my bottles as the formula can be pre made and kept for 24hrs in the fridge.
I only have one bottle a time pre mixed, so as im heating up one bottle, im getting the next one ready with formula and placing it back in the fridge. This gives it 3-4hrs to settle and becomes just like a normal mix (still a bit thicker). We have had no trouble since we have been doing this and it flows well trough the number 2 teat.
Hope this helps you a bit