The only verbal I give before a Strike mechanic is if the batter attempts to bunt and misses the pitch. I will point at the batter and say, "Offer", and then give the hammer. Not sure where I picked up that mechanic, and if it's wrong, oh well.
On a checked swing, there's no reason to do anything special. If you judge the batter did go on the swing, you just give the non-verbal hammer indicating there was a swing, just like you would for a full swing.
Yeah, I know; why don't I just give the non-verbal hammer for the bunt attempt as well? I dunno; it's just a habit I picked up years ago, and I can't seem to get rid of it.