I have been riding and training my horse Sassy in snaffles (twisted, smooth, eggbut). I can tell she is ready for her "step up" bit. She responds well to leg and seat cues, but she is easily bored. What little basics there are to go back and work on with her, you can only work on for so little before she says "...yep no this sucks. Lets do something else. I'm about to have a major mental breakdown." She's a great horse and is way too smart for her own good.
I recently (aka this morning lol) purchased a Simplicity bit, it doesn't seem too harsh but is just a step up from what she has and will help her lift her shoulders more. Going to ride her in it tomorrow and see how she takes it! Classic Equine Goostree Dr. Bristol Simplicity Bit - Horse.com