Follow on to keeping it simple...
Simple works best, true.
But one thing I learned from a few years of wrestling and a lot of years of aikido: If you have to think about the technique, you can't execute it under pressure.
If you really want to learn disarms, you need to practice them until they don't require conscious thought. Even then, your chances of success are far from guaranteed.
But if you have to think about the move, you won't be able to do it, unless you get ridiculously lucky.