Depends what you mean by "milking". You can "milk" yourself or have someone else milk you with any toys or fingers that are big/stiff enough to put sufficient pressure on the prostate to push out the prostatic fluid - this is one form of "milking". Pressure on the seminal vesicles can also push out fluid. This can happen without sexual arousal.
There also seems to be a sort of "milking" where you're at high arousal and fluid is being released - this would be more difficult.