Is lucid dreaming like astral projection in the fact that everyone can learn it?
Or does this require a natural affinity?
Yes anyone can learn it. It really is just about being more aware and noticing the signs while you are dreaming. If you are on unfamiliar ground I would suggest starting with a dream journal to help get you thinking more about your dreams. This may also help with increasing the frequency of your dreams because you are thinking about them more.
There is also the reality check system which helps a lot. The most common is looking at your hands. Frequently throughout your normal day look at your hands and ask yourself if you are dreaming. Eventually, through habit, this will creep into your dreams and can trigger Lucid moments.
Sounds easy enough, thanks a million!