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.
Mike
PS: and a huge thumbs-up for terrysrubberrollers.com!