I think average to above average speed is a prerequisite to becoming a slapper. If you?re just looking for someone to move the runners along, teach bunting to a specific spot. If you?re looking to get a girl on base, then some speed is going to be needed to beat out the throw from the hit that doesn't get through the infield. Who would I pick to "become" a slapper...a speedster, a girl that can't drive the ball, a pitcher who concentrates on her pitching? So, a whole host of players.
I recently started practicing with my daughter on a daily basis, the art of slapping. In her case, she's a pitcher and isn't the type to drive the ball. She has been on base more frequently, getting RBI's & moving runners along than I had ever anticipated. Who said tennis balls are for the courts- they're great for backyard slapping.