Do not, I repeat, Do not try and do something like this all in one sitting, if you get easily tired from doing things such as these you will notice that you'll keep getting tired which leads to getting frustrated. Remember to take a break everyone once and a while to have some fun, eat and drink, and empty your bowels and bladder. When you feel ready, start chopping up your model in any way you see fit. What you're going to be doing is chopping up your model in such a way that every single bone in your pac skeleton will be replaced with something from the model. Go ahead and open up blender and have garrysmod running in the background with your pac3 ready. If you're a masochist and everything needs to be perfect then chances are you're doing this way. You should make the clavs the very beginning bits of the arm. There are two methods for doing this.Įdit: After messing around with clavs a bit more I've learned that you should, under no circumstances, use the actual chest area for the clavicles. Most large models require the clavicles to be pulled out from the body so as to allow comfortable arm space. It is best to get a reference of your model and compare it to your t-pose, if certain parts of your body need to be shortened or stretched, get the reference model close to your normal bone structure and stretch, shrink, or pull on the bones. obj files made in blender and clipped models of your model ( I recommend using a headless t-pose for the clipping). This can be done using a mixture of separate. The main idea of this is that you want to make a model that uses your custom model but has bones. Once you have these things it's time to get cracking away at your sanity. A sharing program that works with pac3, I recommend Puush.A model with humanoid proportions (unless you intend to make custom animations for a model that comes with gmod like D.O.G.

An understanding of clipping models and/or Blender Modelling Program.

A basic understanding of how to use pac3 and change a models bones.

To do so I recommend you use these things:

Assembling a custom model with no bones into a pac3 is quite the feat.

Where to find pac3 in gmod files