Funny, I don't need to cover my brake or shifter constantly, just in case. I move my fingers into comfortable positions, move them back to do their job. I only cover when I believe I might have the need for them, or am actively using them.
Gripshift is a viable option. I use it on my XC bike, as well as a friend of mine (mine is 11, his is Eagle XX1).
I'm the same. There are some comments that question why my index finger isn't on the brake all the time. Well, it is, when I'm descending of course.
But during long, sustained, non techy climbs, I don't find it necessary to hold my brake, or have my thumb under-bar for control. I find it more comfortable to switch my hand position to thumb-over-bar and use my index to switch into a harder gear if the grade incline changes. During steeper technical climbs, of course I hold my bars regularly (thumb-under) for the control.
Long story short, I do use my thumb to shift 80% of the time. But the other 20% during long, non techy climbs, I appreciate the option to use my index finger based on hand position. I know this sounds like peanuts, but I'm sure you fellow riders can appreciate we all have these little habits developed over years of riding which become second nature.