Help with Rigging a R6 Model in Blender

Hello everyone! I am using Blender 2.79 to create some renders for my game icons and such.

I imported a R6 model into Blender and I am attempting to manually attach bones to it so that it may deform nicely when posing (like arms bending, etc.)

However, when testing the rig every now and then, it seems to deform very oddly. What am I doing wrong?

P.S. I know the model is not fully rigged yet, I am just testing with the bones I currently have and it deforms rather strangely.

Before posing:

Various deformations when posing:

Are you pairing the mesh to the rig with automatic weighting applied? You may want to manually paint your bone weights on the model.

Yes, I paired the mesh to the rig with automatic weighting. What does manually painting the bone weights do?

Forgive my ignorance, this is a learning experience for me.