Sandy, I did some quick research to see if there was anything new in the world of chinking. The latest method still seems to be the "backer rod" method. I am enclosing a web site to get you started. Considering your logs are well aged, this method should worek out good.
look up: "http://www.hometime.com/projects/howto/cabin/pc2lc03.htm" to get started. Also, "Log Homes" mag is another source for materials, and methods.