At $100 in value, I would not be in a hurry to touch it.
I lean toward tumbling for toasted wheats. It seems like slow even wear from tumbling smooths out pits and corrosion and leaves a great finish. Of course it removes the patina.
I personally would shy away from using acid on a coin with any value, and if I did use any acid lemon, clr, vinegar, I would soak it in baking soda solution afterwards to neutralize any acid left in pits or microscopic holes. I have seen coins damaged years later by dried residue.
I would try the following methods to experiment on coins with little value that are in similar condition:
-Tumbling
-Fingernails - I get tons of grime and grit off with my fingernails. They are softer than the coin, the same reasoning behind brass brushes and toothpicks.
-Toothpick
-Brass brush a brass brush does wonders on IH pennies. Of course there goes your patina.
-SOS Pad - Steel wool with detergent
-Fine Steel wool
-non-metal scrub pad
If I was going to touch the 1909, I would consider flicking the barnicles off with my fingernail first, then tumbling. Going slow.