Let's say you don't have a partner and want to practice the hold-back method with mastrubation. What is the only way you can do it is by thinking about or imagining some person. Isn't that immoral, as you don't have the consent of the other person.
If that doesn't work, start the tantric process with imagining someone else but slowly start paying more attention to the energy/emotions in your own body during the process. I think over time, it is pretty easy to break the well established link between images/thought of another person and the actual process of solo masturbation.
Yogani has advised to turn whatever holds us back or bothers us into bhakti for the divine!!
dude, your imagination is your most powerful asset. Use it as you wish. Create big, powerful images in your mind. If it is a beautiful woman you are imagining, there is nothing wrong with that. Do not feed any form of guilt.