If any of you have the Mr. S World's Most Comfortable Butt Plug, you may some day face the same problem I have, that the rubber tube section begins to dry out and crack. Before spending upwards of $200 on another one, they can be repaired for about $16! Alas they are slow (6 weeks!) : (
In the mean time I discovered a technique to insert a modestly inflated balloon into the rectum. It is fun enough to share! You should warm up your butt first with favorite toy, and then take the balloon, filled to only your comfortable long term capacity, and twist it in half, or better about 1/3 and 2/3, remembering the direction and number of turns. Then lube up with a silicone-based lube, covering the smaller chamber and your anus. This small part can be stuffed up the butt with one hand, using a bit of a trick. You need to pinch the constriction between the middle and ring finger, cupping the lubed portion of the balloon in your hand. This is slipped in first - next, you need both hands to move to the larger chamber. A modest hit of poppers, or at least a trained relaxation response might help you with what's about to come - squeeze and turn the large chamber, unwinding the constriction and transferring this air up the butt.
Done right, you will soon be holding the whole thing - and off you go! Otherwise, and especially if you are too tense or overestimated your capacity, a slippery balloon will get away from you and pop or bounce along the floor - drat! This does take some practice...butt well worth it!