Yeah, the feeling of the suppository shooting in is the most erotic moment, no doubt about it; you can still feel the suppository is in there for a couple of seconds until it has warmed up.
Glycerin suppositories don't really work for me, which I used to my advantage by inserting 6 of them (they come in boxes of 6 here) at a time just to get that feeling again and again.
With Dulcolax, however, it's a different story, I try to get them in as far as they would go using a vaginal applicator (the effect will be stronger the deeper they go in and the longer you hold them), so there's no shooting or getting sucked in. The urge they produce is incredible and I enjoy every second of it. It's the slow buildup of the urge, each wave is stronger than the one before it and when I finally have to give in and let go it's like some sort of climax.
I ordered a box of Magic Bullets the other day and although they'll cost me dearly including shipping and customs fees I have to give them a try. Allegedly, they'll work even faster than Dulcolax, so to me that's like reaching the next level after 2 decades of oil based bisacodyl suppositories. I intend to insert the first one the old-fashioned way, then push it in with my index finger as far as I can manage.
If anyone else could share their experience with the Magic Bullet here, that'd be awesome.