Jeff;
I suggest trying this method before investing in a ballast spreader tool. I did have one years ago, but it didn't work as well as what I'm using now. (and suggesting that you try)
I use a 5 oz. size Dixie cup with the top bent inward to form a "spout" shape. I fill the cup half full with ballast. Then drag the tip of the spout along between the rails, letting it drag across the ties. This makes a click, click, click, noise, and shakes the ballast out of the cup. Drag this "ballast spreader" fairly quickly along the track and it will leave a neat, continuous, mound of ballast between the ties.
The mound will be higher than the rails, so it will need to be distributed better. To do that, slowly drag an old toothbrush, handle first, along the tops of the ties, & between the rails. (Note: A normal toothbrush, dragged handle first, will fit perfectly between the rails of N-scale track.) (HO modelers can drag the toothbrush sideways)
Just enough ballast will be brushed up over the rails to fill in between the outer ends of the ties. Also the ballast between the rails will be smooth, and flush with the tops of the ties. Make another pass with the toothbrush along each rail, with the toothbrush's bristles straddling the rail, some bristles inside the rail, and other bristles outside the rail.
This pass will level off the outside ballast even with the outer tie tops. It also helps remove any ballast bits from the inside web of the rail where they might be hit by a wheel flange. Touch up as necessary, but this method makes a nice even layer of ballast with minimum effort. Its also fast. In the time I've taken to type this response, I could have ballasted a couple yards of track.
I then LIGHTLY spray water on the ballast to get it just damp enough to stay in place. I find a spray bottle from "I can't believe it's not butter" brand margarine, is perfect for this light spray. Then I dribble on some diluted white glue. Five parts water, one part Elmer's glue, & one part alcohol. Finally I spray more water to let the water/glue mix spread throughout the ballast. If you get too much water, hold a paper towel vertical over the wet spot. Just barely touch the bottom edge of the towel to the area, and the excess water will be absorbed up into the towel.
Regards;
Traction Fan 🙂