Creating a shader for trees... Please help with everything involving shaders!

I've been working on a 3d mobile game for about 4 months now. This week I started adding in all the fun stuff(particle effects/models/ALL ART IN GENERAL). The one thing I am having a really hard time with is shaders.

For my foliage, I really need a great custom shader. I found some posts on custom shader code that uses transparency, and I have also been researching a lot about how The Witness achieved their trees/grass.

So what I really need help with, is somehow getting a custom shader to hide texture planes when they hit a certain angle. From reading The Witness blog posts and several threads on discussion boards, I think that is the way they achieve the soft look in their trees. http://static.gosunoob.com/img/1/2016/01/the-witness-pink-tree-puzzle.jpg

I would also love some direction in learning how to write shaders myself. Because even if someone does manage to help with granting me some shader code that makes this work, I still want to learn the ins and outs of shaders and how I can write them myself. I hate using a bit of someone else's code and not knowing how it actually works... Every video I have seen on youtube so far hasn't really giving me a good grasp on shaders though. They usually skip over stuff I need to know, or go way too fast.

Thanks! -Austin-