I don't use a signal for a joust. Here are some (probably not all) of the informal signals I use.
"2" or lift in my chest: "You might want to call that double/lift."
"2" or lift signal really beating my chest: "Blow yer whistle NOW and call double/lift."
"4" in my chest: "The next contact will be 4 hits on the other team. Usually given after a taped shot, and this is my way of letting my partner know I saw no ouch by the block.
Head shaking no on a ball out of bounds: "I saw no touch."
Back row signal cocked into my chest: "That was a back row player, blow your whistle and signal illegal attack or give me some sort of safe signal."
Back row block signal chest high: "We either have an illegal block or reaching over, you might want to blow your whistle."
Discrete overlap signal given as R or U: "You've got an overlap you might want to pay attention to."
Some people pat their inside or outside legs to indicate a front row or back row setter.
Head nodding affirmatively: "Good call, I completely agree."
(As R) making a slight pushing down motion: "Coach, not an illegal attack because the ball was slightly below the net."
I'll sometimes make what you described as a jousting motion to a coach to signal "ball," as in it was the ball in the net, not the player.
Pat to my chest to a coach: "Coach, I might have missed that one, my fault, I'll get the next one." (Yes, coaches really do respond positively to this...as long as you don't abuse it.)
That's all I've got for now...I'm sure I've got more, but I don't pay attention to them as much.
