I have many animation tracks in my current model. After calculating the bone hierarchy of each track, how do I blend the tracks with each other. E.g Track1 -> BlendFactor 0.8 Track2 -> BlendFactor 0.2 Do i just add or multiply the transformation of Track1 and Track2 together?

never did it. You could see how cal3d does it. It supports animation blending.

exactly the same way you slerp between keyframes....

The big problems you have to overcome are :

a) extract root translation & rotation for each step of the anim and sum them into a position and rotation global var for the character (rotate the last frames translation by the current rot of the character).
b) make sure you sync anims so that feet fall in the same order (i.e. make sure walks and runs all start on the same foot)
c) modulate time so that as you lerp from a walk with 30 frames, it still matches with a run with 24 frames....
d) marking foot falls is useful to modulate time so that foot steps stay in sync. This tends to give much better results.

Ultimately the better the quality of your anim data, the better the results.