You need to use something like the swiffer handle for dusting and use a microfiber cloth attached to is not the duster it is a bit flexible and so gets in where your hand wont

Maybe try a baby bottle brush bent into a curve.

Once you do get them clean, make it a habit to dust the as frequently as possible. It wont eliminate the need for a deep cleaning but it should be less frequent. Thats the problem with these pretty lights, they dont stay pretty without work.

spray vinegar, water dab of dawn, put a towel down and let it drip.

Crystals and kitchen grease should never marry, IMO. "Wet and Forget" has a version of their product that is for showers and I believe it could work for your globes. You would "wet" them in the evening, and rinse them the next day. Since it works on shower glass, it should be helpful to you. I would cover the floor under them with newspaper and towels to catch any drips.You may still have to clean the crystals individually by hand, but the globe should be cleaned more often and this could make that task easier.

https://www.wetandforget.com/wet-and-forget-shower.html