Check out this video posted by a fellow model railroader
This is the second part of a two-part series where I demonstrate the process I used for ballasting the track on my B&M NH Mainline. This video details the four step process shared by Cody and others: Glue down cinders if appropriate; ballast the track center; light ballast on roadbed shoulders; and final ballast on tie ends and shoulders. Video by Steve Tello.