and most umpires understand the the C pointing down towards 1B/3B is a faster/easier way than verbally asking for the appeal. YMMV
I like this. If the base umpire says strike it is harder for the plate umpire not to grant it. This came up in Dad's tournament this weekend. Catcher asked plate umpire....he refused to ask for help. After the game the base umpire said she went."Did she go?", while pointing towards 1st/3rd.
"can you check?" and turn or not shouldn't matter, but not is faster