Hi Ali,
I cannot see any reason why a resistor is not acceptable,
but that doesn't mean that there isn't a reason.
What is used to switch this unit on and off?
Is it a switch ?
If a switch is used to turn this unit on and off,
then with an appropriate switch,
you could arrange,
that when you switch it off, the other contacts
apply a resistor which is not in circuit when its 'ON'
but when you switch it 'OFF' it will drain the 100 MFD.
This would not be "just using a resistor",
as the resistor would not be connected while the unit is
switched 'ON' but would be connected when the unit is
switched 'OFF'
Please let us know why you cant simply use a discharge
resistor in the normal way, that is widely used and
normally quite acceptable.
Regards, John