You can also use a small knitting needle (not a crochet hook!). If it is smooth, long, and about the right thickness, you can gently guide it around the egg from the vent. You go around and around several times, which relaxes the muscles holding the vent closed. Using a thumb to gently push the egg towards the vent so it won't go backwards, put the lubricated probe in until you touch the egg. Make sure you are in direct contact with the egg, with no mucus membranes in between the probe and the egg. If the probe is holding the passageway open with nothing in between, then you won't risk pushing the oviduct in front of the egg, causing a prolapse. You may be able to see the egg itself, or just feel the texture through the probe end. Just make sure it is only the egg that comes out, and no tissue.
Once the closest egg comes out, sometimes the others will work their way down to where you can manipulate them out. Just be careful - I let a reptile vet manipulate eggs once (not using my method with the probe), and I thought he was using a lot of force, although he said he wasn't. Both females were dead within 24 hours. But with the probe guiding the way, and gentleness, I have had good success, although not quite 100% success.
Of course, I must add the disclaimer that I am not a vet, and don't encourage anyone to do this if they don't feel comfortable about it. It is always best to get a vet, or at least an experienced breeder, to help when doing a new procedure. However, I developed this technique on my own through trial and error, and have pretty good results.
Good luck!