Placing ballast is a delicate process. If the layout can be easily bumped into, then I prefer to ballast a section of 8 to 10 inches at a time.

If the layout is stable with little or no traffic next to the layout, I may place the ballast for one whole area first before applying glue. This second approach is faster.

The photos shown here show me doing only a 10-inch section at a time. The darker ties will be ballasted. The other track has already been ballasted. As you can see, the ballast does affect the overall color of the ties afterward.

Applying Ballast
I use Pennsylvania Light Gray (part number 1051) ballast from Arizona Rock and Minerals. This is real rock and it is very fine. Using a teaspoon with some of the ballast on it, I spread the ballast down the middle of the ties.

Then, using a soft bristle brush, I gently persuade the ballast to go in between all the ties. Some of the ballast will fall off to the side slopes of the roadbed. This is what I want.

Lately I have started using my index finger to move the ballast around. This seems to work just as well as long as you don't move your finger too fast (otherwise ballast goes flying everywhere).

This is what the section of ties looks like after the ballast has been spread using the brush. I have found that the rock dust stays on the ties and makes the ties quite a bit lighter.

Next, I use my finger tips to move all the ballast pieces off of the tops of the ties. I keep going back and forth until I no longer feel any ballast on the tops of the ties.

Again using the spoon filled with ballast, I gently distribute some ballast along the slope of the roadbed.

Some ballast will fall on the ties again, so using my finger I make sure that there is none on top of the ties, and that the side slope of ballast doesn't go above the top of the ties either. It is easy to pile on the ballast on the side, and I don't feel it looks right when it is too high.

It looks like this section of track is ready for the gluing stage.

Gluing Ballast
First I soak the area with rubbing alcohol or water. This allows the glue to flow more smoothly, and capillary action will draw the glue throughout the ballast. I use a fine hairspray bottle (you can buy empty ones at places like beauty supply stores, or recycle one from a member of the family). The spray that it produces must be very fine with no drops. The first couple of sprays I aim into the air above the section to be wetted allowing it to gently drift onto the ballast. I continue to do this until I see the color of the ballast changing, indicating that it's getting wet, and it will most likely handle heavier, more direct spraying. I continue to spray until I see that the ballast is soaked.

I pour the previously prepared mixture of matte medium and water using a recycled small glue bottle. The mixture is 50% matte medium, 50% water, and a couple of drops of dishwashing detergent. I place drops down the center of the ballasted track, and have found that capillary action draws the glue all throughout the ballast, even down the sides. I usually let this dry overnight, but it can be dry within an hour or so.

The next day I sand the tops of the ties down a bit to remove any stray ballast that migrated during the gluing process. I use a nail file because it is just the right size for N-scale track, and it has very fine sand paper on one side. You can buy this at the make-up section of grocery stores, beauty supply stores, and even at some general hobby stores. They're only a few dollars and will last for years.

A quick vacuum cleaning removes all the loose ballast.