I haven’t seen this posted clearly anywhere and it is pretty simple. Here’s how to match motion blur. Track a point with a tracker node, pipe that node into the 2d transf pipe of the motion blur 2d node, and then pipe the result into a vector blur node. Connect your source footage to the other pipe on the motion blur 2d node and you ought to see some blur!
The tracker finds the motion, the motion blur 2d converts it into u and v ramps, and then the vector blur actually converts it into blurred footage.
If you have a camera track, then you can swap that and the motion blur 3d in to get similar results.