I believe you refer to the use of misoprostol. It has been used successfully to facilitate difficult ETs but I have no personal experience. More information can be found in the following two references:

J Minim Invasive Gynecol. 2010 Jul-Aug;17(4):449-55. doi: 10.1016/j.jmig.2010.03.015.
Clinical use of misoprostol in nonpregnant women: review article.
Choksuchat C.
Abstract
Misoprostol, a prostaglandin E1 derivative, has been widely used in nonpregnant women because of its cervical ripening and uterotonic effects. A large number of studies have demonstrated its effectiveness in enhancing ease of cervical dilation. This review article describes its pharmacokinetic profile and the relationship between prostaglandins and cervical ripening and uterine contraction and provides a review of the clinical use of misoprostol in nonpregnant women including cervical priming before hysteroscopy, before insertion of an intrauterine device, in endometrium biopsy, preoperatively in myomectomy, and before intrauterine insemination to improve pregnancy rates. Adverse effects are also described.

J Low Genit Tract Dis. 2008 Jan;12(1):24-31.
Overcoming the challenging cervix: techniques to access the uterine cavity.
Christianson MS, Barker MA, Lindheim SR.
Abstract
OBJECTIVE:
To identify cervical stenosis and review medical, surgical, and radiological modalities to access the uterine cavity.
MATERIALS AND METHODS:
Computerized searches of Medline and PubMed from 1996 to 2005 were conducted using the key words "cervix," "cervical ripening," and "cervical stenosis." References from identified publications were manually searched and cross-referenced to identify additional relevant articles. We review relevant techniques on how to access the uterine cavity when cervical stenosis is encountered.
RESULTS:
Many gynecologic procedures require uncomplicated access through the cervix to access the uterine cavity, including hysteroscopy, dilation and curettage, sonohysterogram, hysterosalpingogram, endometrial biopsy, and embryo transfer for in vitro fertilization. These procedures can be quite complicated when a cervix is obstructed. Management techniques described include the medical use of misoprostol and laminaria, intraoperative ultrasound guidance, and operative creation of a new passage. Additionally, techniques for bypassing the obstructed cervix and preventing cervical stenosis have been described.
CONCLUSIONS:
Cervical stenosis can result in iatrogenic complications. Preoperative identification, cervical ripening agents, osmotic dilators, and the use of ultrasound guidance are useful in overcoming cervical stenosis. It is also key to identify those at risk for cervical stenosis and implement preventative techniques as needed.