active bleeder circuit for capacitor discharge
Tried the circuit, with 300K resistor from 60V to gate, and 100K from gate to source, using an IRF9540 P-channel MOSFET. It worked but not as well as I'd liked.  I changed the 60V to gate resistor to 100K, and replaced the gate-source resistor with back-to-back 5.1V zeners.  This worked much better because it tried to maintain a high gate-source voltage even when the supply voltage bled down.

BTW: Disconnecting the supply output from the solenoid unit worked well, with fast discharge of the cap, but disconnecting the input side did not.  I lowered the supply bleeder resistor on the solenoid unit from 10K to 1K, and that worked better for supply input disconnect, but also boosted the supply dummy load to a few watts for each solenoid unit.  Something in between works fine for my needs.