Best way to learn how to scat/trill etc? And why does it seem to come natural to some people?

[MJfan01]

I've been singing for about 6 years now, and have made really good headway with increasing my register and blending head and chest voice etc.

But I've always wanted to be able to do little trills or scatting, nothing OTT, but it is a skill I've always admired in my favourite male singers (Prince and Michael Jackson) and always wished I could pull off.

I have 2 questions:

1. Why does it seem to come naturally to some people? Especially black folks? Does anyone actually know the science behind this?

and

2. What is the best way to go about learning how to do this? Whenever I have tried doing it in the past, I come across tedious exercises of vocal trills which are always out of any musical context and I never really know how to go from these exercises to encorporating it into a song etc. I have also tried slowing down some vocal parts of my favourite songs and trying to decipher some of the tricky timings of the trills that way, but haven't had a lot of luck. 

This is an area I really want to work on. Any tips?