From my experience, making a rig in general is hard enough as it is. Even though there are tutorials one mess up can ruin the rig making you have to start all over again. In addition, some parts to rigging don’t want to work properly making the rig go haywire. What I found challenging was trying to do the skinning and trying to parent the joints with the controllers. I found this to be hard parts because you can’t minus the paint from a certain joint, you can only keep adding and work from there. For the parenting the joints, that was hard because you have to add attributes to certain joints that corresponds the action you want done. What I found to be the easiest was placing the joints in certain parts of the model. I found that to be the easiest part because of how it was basically following common sense. By common sense, I mean how what spot is appropriate for the joint to the part of the body.
-Try to break the connection for the facial expressions to work
-Do more painting with the skinning weights for the joints