How do you create a tree for terrain paint using blender, with standard shader?

Hi, I created some tree models using blender, but when I imported them to unity I couldn't paint them on the terrain unless I extract materials and set the shader to Nature/Soft Occlusion shader.

Well, unity indeed specifies this requirement in terrain trees documentation, but this shader doesn't fit my game environment. Moreover, I was using a free tree asset for terrain plants, and their trees don't use occlusion shader but still can be painted on the terrain.

I wonder if there is any step by step tutorial to create a tree from scratch? Thanks in advance!