Note: this is solely for cases where mushed bananas are acceptable/desired
I often make bananas into banana bread, and what I usually do is peel them into a gallon ziploc bag. Next, I mush them inside the bag, then evacuate all the air and squeeze the mash towards the bottom of the bag (and I like to roll it up to help it stay nice an sealed). You can do this one at a time as you collect overripe bananas, or in a group.
This lets you have relatively little browning and also have pre-mashed bananas on-demand.
Additionally, as you add bananas to the bag, use a Sharpie to tally how many you've put in the bag. Then, for banana bread (for example) once you have however many are in a single/double batch you can set the bag aside and start on a new one. You then have a pre-measured quantity of bananas ready to go, and you can even cut a corner off of the ziploc to make it function like a piping bag for mushed bananas.
This works great if you want mushed bananas to bake with, not so well in any other use-case.