You should likely be able to clean it out, though I can't say how accessible the inside of that button array is. I didn't find any proper teardowns of the Scimitar Pro RGB to show exactly how to disassemble it, but its internals can be seen in this review...
http://technewsexpert.com/corsair-scimitar-pro-rgb/
The screws that you need to remove are apparently hidden under the four glide feet on the underside of the mouse, which you will need to peel off to access. Typically, those feet should be able to stick back on when you are done and have the thing closed back up. The residue might clean off well using isopropyl rubbing alcohol. Just be careful to try not to break anything, as some of the internals, like those ribbon cables connecting the side buttons, might be delicate and you should be careful not to tug on them too much. To get into the button area, I suspect you might need to unclip those little black plastic tabs shown above, below and to the right of the ribbon cable in the second internal image in that review. There might be more screws holding those parts together too. Be careful not to lose any little parts, and you might want to snap some photos as you go to help you get everything back together properly.
If there's any residue inside the actual clicky switch mechanisms below the buttons, it may not be as easy to clean them out. If they're gummed up inside, you could maybe try using some isopropyl alcohol directly on them, but make sure everything is completely dried out (perhaps overnight) before plugging the mouse back in. And yes, it should be unplugged when you're working on it. : P
It's possible that dismantling the mouse could result in you breaking it, but it might be worth a try if the mouse is becoming unusable, or you are otherwise just willing to risk it.