I had good success using a carpenter's pencil as a substitute for the lock bead installation tool. (You can get them at any basic hardware store.)
Sharpen it to a reasonable "point", then dull it back so that it is smooth and has no corners. The graphite works well as a lubricant for the rubber.
They cost less than a buck, and when you're done, you have a great looking back glass and still have a carpenter's pencil!
Bill
