Insight from yours truly-a retired professional glazer.
NEVER use ANYTHING steel-screwdriver, putty knife, etc.� Do so and you're DOOMED

Use multiple "bones"-they're the right tools for the job. Have 3 or 4 on hand to "spread" the load.� Pull the bone toward you, don't push-pushing increases the pressure on the glass.
Use the slippery, messy soap solution tho it's a PITA to work with and clean up. Regular old Windex in the spray bottle works well and leaves less mess and hey you'll want to polish your new glass when done anyway, right??
Handy tip..try to do the work in a heated environment (I know, it's easy to say this time of year) making sure your rubber gasket is warm, soft, pliable. Cold, hard rubber greatly increases your chance of failure.
Hope this helps.. Rick