Most seem to suggest a 4ft level placed against the rear tires. I have gone to that method and feel like my toe and scaling has gotten more consistent. I'm too cheap to buy a accutoe or steering lock to put on this old banshee.
If you have a way to make your own toe plates, back in the day I had two pieces of angle 12" long, notched and drilled them so I could bolt them on the hubs. Measure at the front and back to see your toe.