Selfing is simply using pollen from the same plant instead of from a different plant. Whether the pollen is from the same flower or a different flower on the same plant doesn't matter.
The possible upsides to selfing are being able to propagate a rare plant if no other is available, possibly maintaining or enhancing the good traits of an exceptional plant in the next generation, or if the plant is a hybrid you might get lucky and come up with a better combination of the traits of its parents.
The downside is that any bad traits are just as likely to be maintained or enhanced, not just appearance but health and vigor too, and you lose genetic diversity which is eventually a dead end in terms of breeding.
As far as why your attempts have not been successful... Are you sure you understand the anatomy of the orchid flower and getting the pollen to the stigma of the flower? Are you possibly using flowers that are getting too old? Is the plant really strong enough to carry a seed pod?
Are you sure you understand the anatomy of the orchid flower and getting the pollen to the stigma of the flower? Are you possibly using flowers that are getting too old? Is the plant really strong enough to carry a seed pod?