Scott,
I paint full strength white glue in the immediate area around the slide switch and apply ballast. When this sets up, I then can ballast the rest of the turnout and not have to be so worried about ballast getting inside the slide switch. Since I have been using just diluted white glue (2/3 water 1/3 glue) to glue the ballast down, it doesn't seem to stick to the turnout parts, so I haven't found a need to use oil (as some do) to keep the turnout free.
Hope this helps,
DFF