We are in the process of redoing the ballast on the club's modular N Scale layout (8'x16').
After 4.5 years of bouncing in the back of a pickup truck to 5-6 shows a year, things tend to fall out.
We treat it as a 2 man, 2 phase job....
Phase One: One fellow pours the ballast using a plastic spoon, the other fellow comes along with a small brush and spreads the ballast out.
Phase Two: One fellow goes along with the eye dropper and soaks the ballast with the dilluted glue with detergent solution. The other fellow comes along with his fingernail and makes sure the inside of the track is ballast free.
One fellow can do it, but it takes alot longer, you can really only do 3-4 feet at a time if you are alone.