Yes, absolutely it's possible. Medically speaking it's called rectal stimulation. I have had to do it many times, providing I have a doctors order of course. To do this is simple, and I suggest using only your fingers so you keep and maintain a direct feeling of the inside of the rectum, and yes, you can use something like an enema nozzle, but I would never suggest using a glass thermometer, but again, for best results use gloved fingers or a finger is usually enough.
Lube up your finger/fingers well, enter slowly, and slowly and with steady light to medium pressure rotate just your finger around on the inside of their rectal walls. This will be all that is needed. Depending on the patient and other variables, the time it takes to produce stool will in fact vary. Once you feel stool starting to come down, slowly back your hand out, but continue the stimulation.
At this point you have two choices. 1) Back out completely and let your patient go and push it out them self, or 2) manually remove the stool yourself.
On my real patients, they usually can't get up and go, so I will usually manually remove the stool myself. It is a good idea to encourage your patient to help you with the process by pushing if they are able, but remember to have them just push, NOT strain, especially men.
And ladies, if you are rectally stimulating your man, as I said earlier, use light to medium pressure because too much pressure believe it or not can and will cause them to die, and yes, I am dead serious.
Also another nursing hint/tip, if you are inserting a suppository as in what stikn was talking about, remember when inserting a suppository be sure to place the suppository against the rectal wall. A suppository has an ingredient in it that when it melts will produce peristalsis, in other words, it will make the walls of the colon contract, which is how and what makes the stool come down and out. If the suppository is stuck up inside fecal material for one it probably won't melt in the first place, and for two, even if it does melt, the active ingredient in it that produces peristalsis isn't going to reach the rectal wall to produce the desired effect, or results. So keep that in mind. Actually, on a side note, when I have nursing students, that is one of the main things I tell them because that isn't taught in nursing school which doesn't make any sense to me at all because medically speaking, a suppository that is given that has a medication in it, no matter what that medication is, whether it's to produce peristalsis or if it's Tylenol to bring down a fever or reduce pain, has to be placed against the rectal wall to melt and be effective. They teach you how to properly give any and all other types of medication and their proper routes and what not, but they don't teach you that one crucial detail.
Hope this helps?