Hello there, first off i must say i absolutely admire, and appreciate your works. Thank you for allowing us to play with such quality models and outfits for SFM with ease and look forward to more content. I wanted to ask what advice or direction you may have if someone like myself wanted to do the same, and get started on making custom models for sfm or mods for other games. Where should i start Blender? Thank you.
Learn the fundamentals of your program of choice. Learn the fundamentals of the pipeline to get models from that program into Source. All of this is available online in droves. Then start by decompiling, editing, and recompiling models. Slowly build up your confidence and experience with doing more and more elaborate edits.