Like Mer said, a milling machine can basically do the whole thing. If you start off with aluminum or brass, you can make bigger cuts faster. That's if you really dont' feel like standing around for the cutter to go through steel. 303 machines well too. I used that for the handles that I'm still in the process of finishing. As far as inserts go...I would hold off on that for now. That is if you're just going to make a sample balisong. The reason I say that is because if you are going to decide to put on inserts on the final run/piece, that'll only require a couple of passes on the milling machine to make the "slot" but you'll also have to spend a lot of time getting your insert material down to the exact size so it fits evenly and flush. Then you'll have to spend more time to get it even with the rest of the handle. Basically that equals a lot of sanding and time, unless you have better equipment. I don't, so I had to hand sand everything :barf:
This is just my opinion from what little experience I have. Good luck to you and please post pics when you're done. Or better yet, how about pics of the processes you went through in making it come to life!