The right sign for "baptize" depends
on which church you go to and what manner of baptism your church uses.
In each version of the sign "baptize" the verb form is generally done with a
single movement and the noun form is done with a double movement.
The general sign used for baptism by immersion is to use two "A" hands and move
them down a bit as you turn them sideways.
Another form of baptism is to show the sprinkling of water onto the head. In
this case, you hold your hand as if sprinkling your own head.
Another sign for baptism is to show the sprinkling of water onto an infant: