3rail 2 posted:Oh, one more thing...
After you place your ballast and are happy with the location....
Literally SOAK IT with plain water in a spray bottle. Again add a few drops of dish washing soap.
If you think you soaked it enough, do it again for good measure. Then apply your glue mix from a SQUEEZE BOTTLE. Do not try to spray it on.
Donald
Excellent advice. And, a few more points to add/clarify...................
Plain water with a few drops of dish washing detergent acts as a wetting agent - it breaks the surface tension of the water. Also known as "wet water" for short.
Squeeze bottle is correct. A 50/50 glue water mix has far too much glue content in it to properly run through a spray bottle.
Elmer's glue is a lot more water soluble after it is dry than matte medium. If you ever want to revise, replace, or remove ballasted track, simply wet it down with wet water and it will soften up considerably after a very short while. Matte medium is pretty much water-proof after it is dry.
If you're squeezing out ballast glue and it starts beading up and not soaking in, don't panic. You probably didn't get the ballast wet enough with the wet water. Simply go ahead and spray some more wet water directly over the beaded-up glue, and watch it suck right in. 
