Mainly, what programs? Commercial programs are not an option for me, so I was wondering if one could use a free program, like Blender, to create models. Then, of course, how to convert to .nif to finalize things in NifSkope? Are there any tutorials or guides that I should look at?

I am sorry if this seems like a load of questions, or if this is in the wrong section, but I have some basic knowledge of 3d modeling, and this seems like a very useful skill, both for my own projects and to create things for the bigger teams, so I am rather interesting in learning.