Mr. P makes a "Scum Fly" that has caught a number of grass carp for him. I tied one up. UGLY thing! I haven't used it yet. I've only caught 3 grass carp, all on flies. One was on a green (mallard) boa yarn leech. One was on a yellow boa yarn leech. The third was on a white "puff-ball" bread fly.
If you aren't too proud about how you get one, I found it interesting to ready recently that banana peels seem to entice grass carp into striking? One public pond I fish for bluegills has some nice grass carp in it. When they are in the shallows, I almost never see them before they see me and dart for deeper water. Spooky buggers! I was recently informed the City stocked something like 60 grass carp in one of their ponds. That was a rather clueless idea on somebody's part...but might provide me some interesting opportunities in the next couple years, even if the fish won't be very large.

For the gar...tie up a nylon rope fly...6" long. Comb out the fibers at the tail of the fly and singe the tips with a lighter/match. Color the head red. Cast ahead of gar that are near the surface. Bring the fly in front of the fish. They will usually follow. Keep the fly moving. When they grab it, let them snap their jaws a few times so their teeth get tangled in the fibers. Then start trying to bring the fish to hand (but wear a glove...or use a fine-meshed net). Some will still get away.

Common Carp...I'm still learning.