To sign after, take your non-dominant hand and lay it flat in front of you. Then take your flat, open, dominant hand and make the motion of sliding it once on its pinkie side above and across the non-dominant hand, forming a noticeable arc in the process. It is as if you are in a car, starting on one end of the street, and after some time, you are on the other end.
This sign should not be confused with wood, where the dominant hand "saws wood" several times.
Teach your toddler the after sign in the context of a series of activities or places you are visiting. This is especially useful if you need to tell them you are busy -- or if an activity is impossible at the moment -- and that you will attend to their needs after a certain time.
Teach your toddler the after sign in context, when you are explaining the right time to do something, or when you are going somewhere and you want to explain relative locations.