personally I discovered I could improve balancing when I stopped using gimp with all of its sliders and curves and other tools. I guess it is somewhat intuitive, since I feel pixel art technique is improved when you stay within very restricted tools. To me , all of the options and index sliders for color balancing just pixels devolves into an obsessive process that forgets the figurative bigger picture. I think it can be helpful, for instance to boost some saturation or change hue in a snap to immediately alter the mood from say lively to grungey. Overall though, I feel if this was necessary, an error was made in the beggining stages, akin to progressing with a piece that has poor anatomy. I agree with Dawnbringer that RGB sliders are perfect; the pixel art tool equivalent to say your bucket fills and line tools. It's obviously not about discovering that "perfect shade or value", but rather just how the colors harmonize, and rgb sliders and no more work for this mentality.
what I love about grafx2 is a new piece will automatically have a wide range of colors in the menu to choose from right off the bat. It's very easy to pick the base color by eyeballing and selecting one of these colors and I don't have to worry about focusing on anything but how the colors I choose play rather than tweaking endlessly. Then the rgb sliders just help me think of the colors as you would with a handful of real life pigments, rather than the thousands of colors drawn in digital painting, and the million colors implied in color index tools. Once I already become content with the colors I manually harmonized, then the sliders are a good way to refine. That's how I see all pixel art processes. Make dirty > make dirty work > make dirty pretty.
I also like the rethinking of the concept of hue shifting. Hue shifts in ramps should receive much of the attention in terms of how shifts in hues harmonize not just the ramp it's on, but to the piece as a whole. Simply having a base color and doing the method of " increase value and make yellower or decrease value make bluer" is not a good approach to those seeking more "magic" to their colors in pixel art. I suppose this approach isn't optimal simply because you can't mix pixels exactly like you can paint, and does not consider how colors and ramps flow more organically into each other. It also just leads to unoriginal colors to beginners.. The Crimson Reds, the oranges, sunflower yellows and deep purples beginners choose often when learning hue shifting begin to get old and unexpressive quickly. I find a lot to learn in how Helm, Adarias, Dawnbringer and Jinn select colors. Regardless of the methods used, an end result I often see is surprisingly outlandish color combinations, and blending (as well as smoothing with good understanding of neutralization and balancel) which actually evoke how artists translate real life nature to canvas painting- there's a quote that says to throw more red in your stem and throw more green in your rose to make it sing in harmony." What I see in these great pixel artists is this sort of mentality translated seamlessly to pixels by way of refined color choices, but also just good pixel technique. I think this is where hue shifting necessitates the utmost care, since the goal is a small palette, and again pixels can't blend as infinitely as paints. . The more ramps can link and intercept (maybe ramp blocks could include the same ramp jutting from multiple areas to demonstrate this), the more open is the door to combine and harmonize colors in outlandish, yet entirely more organic ways.
In summary, I think an aid is to actually REMOVE the training wheels of index sliders, or at least develop a process in which you can think more about organic, inter- hue play and ramp connectedness.
I think a goal to achieve by pixel artists is somewhat to understand how it can be possible to translate an organic harmonizing of hues to a small number of colors that can not mix like real paint. Perhaps at once it is not only about trying to simplify the process into the restrictions of pixels, but to understand deeper the complexities of color, so that the artist can learn how to tweak the process to fit into said restrictions.