Just as an aside, for what it's worth..., I was watching a video about the dangers of these DIY devices built from old transformers out of a microwave oven, that people are using to do 'wood fracking.' They burn fractal patterns into wood using very high voltages. And people's hands from time to time, with electrical burns, according to the video.
I could tell the guy narrating the video seemed to me to know his stuff, and he even mentioned to never use those capacitor leads with resistors to discharge a capacitor. He specifically referenced using a well-insulated screwdriver (with rubber gloves on of course.) I don't recall him saying whether that applies only to capacitors that have been removed from the circuit, but his comment struck me as disagreeing with some replies here, in the context of safety.
And FWIW, my pic of a screwdriver was a half-joke. But I too have discharged A/C capacitors with one, after disconnecting the leads. It's how a heating and air tech friend of mine told me how to do it. Maybe it's different in guitar amps...?