AZ vacation BNSF Phoenix sub in Williams next to GCRY

I am from Middletown,Nj and will be going on a vacation to Arizona on August 20th for 6 days and will be in Williams,AZ August 21and 22 I know the BNSF Seligman Sub is just down the road but when is it the best time to go to see a BNSF train run on the BNSF Phoenix sub next to the Grand Canyon Railroad and next to the station in Williams? I have been looking these things up but cannot find anything. Also is there a spot that has a paved road and a place to park in Williams or just out of Williams on the Seligman sub and when is the best time to go to see trains on the Seligman sub in Williams and Flagstaff? Also does anyone have scanner frequencies for these lines? Thank you If anyone could answer these questions it would be greatly appreciated because I know nothing of Arizona railfanning hahahaha.

Here is a link to Brett Wirick's website. Check out the Maps and Information section for the BNSF's Seligman Subdivision. See http://www.trainweb.org/brettrw/

Ed in Kentucky

Thank you.