Oh, if it's god a good T&T program you're in exactly the right place!
I'm hesitant to make suggestions about training this, because so much of it is dependent on your current amount of power, your individual quirks, your coaches' spotting ability, etc. So I'm not going to give you pointers on how to get over that initial hump and add the second flip for the first few attempts; all I'll say for that stage is talk to your coach, and either you trust them or you don't.
Having said that, here are a few things that will help:
1) Once you take off, you are committed. If you get lost in the air, don't bail; tuck harder; it's almost always safer to overrotate a double than to underrotate it.
2) Once you get past that initial hump of adding the second rotation, the next step is to pay very close attention to what you see every time you do it. You don't want to go up, flip twice, then spot the landing; you want to flip once, see the landing, flip again, see the landing again. Spotting the landing between the first and second flip will do wonders for you, making it much less scary and much more consistent.
At first, you'll probably just want to watch for colors. Hopefully the floor and ceiling are different colors, so try to consciously look for the floor color in the middle of the skill. As you train your brain and your eyes to do this, eventually you'll reach the point where you can clearly see the floor in the middle of the skill.
