I clip one end of a wire with alligator clips to the chassis, then slip the other clip under the anode cup. Once I'm sure it's made contact a couple times, I bend the cap back a bit and attach the clip to the connector, just to make sure it stays discharged.
It's just a scope CRT, it's charged to a somewhat lower voltage than a bigass television tube and has less capacitance. You still don't want to go sticking your tongue in the anode port, but other than that there's not much to it. Ground it for a minute and you're done.