Start off Friendly
A dog is not called man’s most loyal creature without a reason. Your dog really does trust you with his life and that is why you should show that you appreciate his trust. The best way to start off is friendly. Keep it plain and talk to him, pat him to show that you really want it to be better for him and take his suffering away.
Show the Enema
Surprise is not what the dog needs right now so it is best that you allow him to see the enema kit and let him sniff it as well. Grease the tip of the enema to make insertion a lot more easier for you and the dog as well.
Slide it in
The next step would be to gently lift his tail, if he has one, upwards while talking to him to show that you are taking as much care as possible. Slide the top of the enema syringe into his rectum now while holding him in your left arm. The dog needs to be comfortable with you and not being brought up that way will force him to resist your move.
Squeeze the contents of the enema into his anus now, but do not take it out just yet. Leave it in there for a few moments while rubbing his stomach to make the process easier for him. It will not take long and you should observe whether he does defecate within five minutes or not.