I have no idea just how the walls could be insulated, but I think you will find that it is more of a job than you want to take on yourself. Several years ago, I wanted to blow insulation into the attic of my shop. I priced the insulation and thought I had a real deal because the dealer selling the insulation would give me free use of the blower. Before I took action, I called a professional insulation company for a price. I just wanted to see how much I was going to save by DIY. Ha! I learned that they would sell me the insulation and do all of the labor to install for a few dollars less than just the insulation was going to cost me. Now this was just an attic, not walls, but my point is, this might well be something you would want the pros to do. At least get them to give you an estimate.