I do not know if this is the easiest way.. let's give it a shot... hummmm
I will start with the map as background if the map moves is one story if the map is static that will be a much easy story.
Say is a USA map & we gonna connect LAX - HOU-MIA-NYC
1 I will go to (efx bin)color and make a solid red frame.
2 Then I will crop it to a thin line that fit nice in the map.
3 Overlap the line and the map.
4 Drag the line and one edge touch LAX and crop it to HOU
5 key frame the croping (say zero point to the HOU point)
As the playhead moves trhu your clip the line will form LAX to HOU
Then repeat the process from HOU to MIA and so on.
When the line arrives to the city you could add a dot on the city (meaning we arrive!) (another layer) To get a nice dot select OPTION + 8 and there's the red dot! You could also glow it when it arrives wit keyframes or with an overlaping of a second bigger dot more soft.
You may also have to do multiple layers on the red line from city to city.
Also i you add a bit of gaussian blurr say 0.33 over the line it will give you a more glowy or soft edge that a harsh one.
This instructions are a rough but is the concept of what I would do.
If the map moves that will be a challenge to syncronize but if you can understand this idea the moving map could be done too maybe in parts.
The magic is on understanding the keyframes and the cropping there's the trick!
Let us know if works like Doctor Jones finding treasures.
Daniel
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