11. Create a new material according to your need. In this case, I created an opaque material:



12. Add a "mix" map to the "diffuse color" channel (forget the other channels in the illustration for the time being). Add the first image (front / shoelaces) in the top slot, the second image (lateral) in the slot in the middle and the b&w mask in the last slot.
The material editor will show a similar screen:



13. Configure the parameters of each one of them according to the illustrations below (front, side and mask, respectively):








14. Make test renders to verify if everything's ok (rarely it will look right the first attempt). It's possible that you have to retouch the mask painting until the "blend" is perfect.




15. After you're sure everything is ok, you can collapse the object modifier list (along with the uvw modifiers) and do small adjustments to the model, if you need to:




16. Here is the model after the uvw mapping applied and with addition of some irregularities to the boot mesh:



17. Here's the final version of the boots, mapped without "amendments":