the "easy" way is to use volume automation. Much more flexible and easier to undo.
Or use a compressor.
Volume automation is great until you decide the bass is too loud and you must select all the automation and lower it, since the fader is now no longer available.
not any harder than deciding the single region that you just changed with your "gain plugin" is too loud or too soft.
just select all your volume automation and trim it down with the trim tool. Or use the trim automation