This technique works well with M.E. Flex Track. Thanks to Chris Webber for creating the video. I've gone one step further by using a squirt bottle with a little liquid detergent and water. Spray the rail, wait 10 to 15 seconds and begin working the track. When I'm done I rinse it off and let it dry. Also assures the rail is cleaner for applying paint, weathering, whatever.
https://www.youtube.com/watch?v=y_R-j8QJJnk
A word of caution. If you make these blocks please make sure the grooves aren't so deep that the cast in spike heads are destroyed/knocked off. Trust me on this, it's a bad thing.
Jay