The overwhelming best help with TTL flash is to just watch your results (rear LCD), and then and there, simply do what you see you need to do (flash compensation) to make the second one right. Or the third one if necessary.
Not nearly as bad as it sounds, because if we think about why, then experience soon often lets us take a shortcut, we can see the subject and already recognize what is going to happen when we walk up for the first shot. We do have to think about it a little more, but that is our job. It is really pretty easy, just make it look like you want it to look. If this approach is ignored, we may not like flash very much. But if we try a little, if done right, it is wonderful.
TTL is not about the flash brand, the camera meters the TTL and just sets a power level in the flash unit. The flash merely responds, and flashes. But "experience" means there are a few things that help when we know what to watch for. How meters work, what the meter is actually doing. That white things will underexpose, and black things will overexpose. That if significant ambient, TTL BL mode is reduced to be fill flash, but TTL mode comes ahead on strong regardless. That unlike sunlight, flash falls off fast with distance (flash can only be "correct" at one distance), which greatly effects exposure. There is more to it than just being point&shoot.
All that is the physics of light, just how things are, regardless of brand of our gear. Same kind of thing as knowing we cannot take our hands off the wheel when driving down the highway, it won't go straight very long (regardless if we rather it would). We learn what to do and what not to do.
But the thing that irks me is the D-lens distance thing (which is Only about TTL BL direct flash). That is planned design. Works better with prime lenses, but we use zooms today. Nikon surely knows this cannot and does not work well with zoom lenses, yet they do it. If this is something new to anyone, see at least the pictures at
Nikon TTL BL flash - D-lens distance data accuracy
