The first step in getting a submissive male to take an 18 inch dildo anally is to make sure that he is properly prepared. This means that he needs to have an empty stomach and to have showered and cleaned himself thoroughly. He should also be relaxed and comfortable.  The dildo should be very clean too, to avoid bringing in bacteria into the colon.

Start with a long tapered one like this:

Once the submissive male is ready, the dominant female can begin to get him aroused and relaxed. She can do this by using a combination of physical and verbal stimulation. This can include touching, kissing, and talking to him in a soothing and reassuring way.

Once the submissive male is aroused and relaxed, the dominant female can begin to prepare him for insertion. This can be done by massaging his anus with a lubricant and by gently inserting a finger. This will help to relax the muscles around the anus.

Once the submissive male is relaxed, the dominant female can begin to insert the dildo. It is important to start slowly and to use plenty of lubricant. The dildo should be inserted gradually, allowing the submissive male to adjust to the feeling of being stretched.

The anatomy of the body that the dildo has to pass through includes the rectum, which is the innermost part of the large intestine. The rectum is a muscular tube that is lined with mucous membrane. It is important to note that the rectum is not a straight tube and has a number of curves and bends. The dildo needs to be maneuvered in order to get it past these bends and curves.

As the dildo is inserted, the dominant female should monitor the submissive male for any signs of pain or discomfort. If he feels any pain, the insertion should be stopped and the dildo should be slowly and carefully removed. If the submissive male is comfortable, the dildo can be pushed in further, up to the 18-inch mark.  To get it this far the dildo passes through the colon, it will pass through the ascending, transverse, descending, and sigmoid sections of the colon.

It is important that when you hit the original wall, this is mostly likely the entrance of the sigmoid colon.  DO NOT FORCE THIS.  Tickle it with slow back and forth motions.  ALWAYS STOP IF THERE IS PAIN.  This will take several attempts, there are dildos specifically that will help you with this like the serpentine dildo from Mr. Hankeys toys like the one in the above video.  These are not as girthy, and can have a softer material for navigating into the colon.

The dildo has to pass through the anal sphincter, the rectum, and the sigmoid colon before reaching the large intestine. As the dildo passes through the anal sphincter, the dominant female should use her hand to help guide it in. Once the dildo is in the rectum, she should use her hand to help it pass through the sigmoid colon. Finally, the dildo should pass through the large intestine and reach its destination.

Once the dildo is fully inserted, it is not advisable to do any fast thrusting.  Take it real slow.  Over time and many sessions your tolerance will build up.  Do not rush this.

Once the submissive male is comfortable with the size of the dildo, the dominant female can then increase the size and length of the dildo. This should be done gradually and it is important to always monitor the submissive male for signs of pain or discomfort.

By following these steps, a submissive male and a dominant female can successfully get the submissive male to take an 18 inch dildo anally. It is important to remember to always use plenty of lubricant and to monitor the submissive male for any signs of pain or discomfort. female can begin to introduce the dildo. She should start off with a smaller dildo and then gradually work up to the 18 inch one. As she does this, she should use her hands to stimulate his anus, making sure to use plenty of lubricant. This will help to relax the muscles and make it easier for him to take the larger dildo.

With patience and practice, the submissive male should eventually be able to take the 18 inch dildo anally. This may take some time and should be done at a pace that is comfortable for both parties.