I use a 1-2-3 approach to get rid of any flavor of some of my "heavier" flavored liquids: I use a very short piece of latex or silicone tubing (depends on diameter of atty), connect that to a luer lock syringe and shove the atty (
threaded part pointing away from the tubing) into the end of the tubing.
1. Thoroughly rinse using lukewarm water with just a bit of Dawn: Hold the atty's threaded side into the water and pull plunger of syringe, empty out over sink depressing plunger. Repeat a few times, then clear rinse with lukewarm water until no bubbles show in the syringe.
2. Pour a small amount of high-proof alcohol into a dish, lower threaded part of atty into that and pull/push plunger several times.
3. Final rinse: Use clear lukewarm water or - and better - distilled lukewarm water. Lower threaded part of atty into it and pull plunger, empty out over sink and repeat until water is clear in the syringe.
Works well on cartos too.
What flavors are you trying? Did you test any yet?
Happy new year!