We have two large O scale 2 rail layouts being built in Williamsburg, VA. Construction started around 8 years ago. Both model The PRR but in different regions. A month ago I suspended operations on my railroad to ballast and scenic the Pittsburgh Div. While necessary for a protype look I find ballasting takes a lot more time than one would think - and it can become boring if you're doing hundreds of feet of track at a time. Fortunately done right it will last the life of the railroad without more than vacuuming every couple of years. I'll post some pictures and a video of Horseshoe Curve operations when it's done - hopefully before Fall.
Ed Rappe
Ed, we developed a technique that, while a bit messy because of the water involved, is pretty fast. I would not recommend this on unsealed Homasote, though, because of the high volume of water involved.
You need a quality 4" paintbrush to tamp and shape the ballast and you work sections of about two to three feet. During the ballast application/tamping, you work away from turnouts and do those the hard way to protect the points and throw bars. Forgive the heckling in the video, but the gluing technique is what speeds up the process. The glue mix is 2 to 3 parts water; 1 part white glue in a re-purposed mustard bottle; spray with wet water before and after applying the glue.