For ballasting I use sandpit sand bought from ToysRUs before it disappeared. It is reasonably coarse so can pass for ballast in n gauge. 

 

One of the things I do not like about commercial N gauge track is the depth of the sleepers. I therefore wanted to use the ballast to hide this depth consistently. After some experimentation I came up with a scheme to achieve this.

 

Once the track was laid, I lined the edge of the sleepers with evergreen 1mm quarter-round StripStyrene. The depth is just a little lower than Peco code 55 sleeper depth. An example of this can be seen in the attached image showing a bit of test track. Ballast was then glued to the edge strip using water proof wood working adhesive painted on to the strip with a fine brush. Once this was dry the remaining gaps between the sleepers were ballasted in the traditional way by spreading ballast carefully and setting with watered down PVA with a little washing up liquid to kill surface tension. This creates the illusion of a ballast shoulder on which the sleepers are resting. 

 

It was then airbrush weathered using a range of colours but mostly Precision Paints Track Colour.

 

 

EE D6827 has no real business being there. I just like it!