Personally, I would NOT spray graphite powder on anything in a tape machine. Fine if it falls off of the tape that I installed, but I would not add my own. Especially that Roland where the tape is not in a cartridge.
The first thing is to do basic tape machine maintenance- remove the tape from the path and clean the path, 100% alcohol(not from the drugstore!) for the metal parts and Athan pinch roller cleaner on the pinch. Just a mildly damp Qtip for the alchohol and a good paper towel for the pinch cleaner. A small demagger for cassette decks will do the demagging job. Then you have to determine what is causing the binding- is it a gooey pinchroller, bad pinch tension, or worn tape? There might be a tension spec in the Roland service manual, but feel is what most techs use.
The parts were still available from Roland as of 2 years ago when I bought tape and a new pinch roller.
Regarding the tape, they used "cart" tape that was lubricated with graphite. One Echoplex user I know uses degaussed 8 track tape from barely used tapes he still finds at garage sales. Another source is old stock from radio stations.
That is a great unit. Try to find someone with studio tape machine skills, who would have the necessary tools and cleaning supplies, if you don't want to forge into it yourself.
PS: and a huge thumbs-up for terrysrubberrollers.com!