I want to start by saying, there might be a better/easier way to do this. But I don’t know it, this is how I do it.
This tutorial is somewhat based on that you know your way around 3ds Max a little bit.
First start by selecting the model you want to edit.
Then convert it to an editable mesh.
Add a smooth modifier (and select the “2” for best results)
then add a “Edit Poly” modifier.
Mark the areas toy want increased polycount on with the vertex selection tool.
Then click the MSmooth button.
Then convert it to an editable mesh again.
Then add a Smooth modifier.
Then we’re done for the most part. Now we’re just gonna fix the most common error while doing this.
Use the vertex selection tool and select the verticies surrounding the hole, like in the pic and press the “Selected” button under “Weld” with the 1.0 setting.
Repeat this on all the holes and archive SMOOTHNESS!
Then you can go on and continue as usual with weighting and such.
Hope this helps 🙂