Annulments due to lack of form are typically straightforward and relatively quick. The parish at which a person is baptized is supposed to keep records of any subsequent Sacraments. If there were a dispensation, the marriage would be recorded there. If the parish records don't show a marriage that basically proves it did not have correct canonical form.
Okay, I didn't think about that part, that is, one's parish of record (where they were baptized) having all of that information. I can only hope that this system is as efficient as it's supposed to be. Would be nice if all of this information were in some consolidated database.
I struggle to understand why a faithful Catholic would ever have to seek dispensation from canonical form. If one's prospective spouse refuses to marry in the Church, preferring their own sect's ministrations,
is that really someone you want to marry in the first place? And the $64 question, what if you have children, you die or become incapacitated, and you're looking to your spouse to bring up your children in the Faith?
I can't speak for women (who seem to be more open to marrying non-Catholic spouses, guess they think "maybe he'll convert in time"), but no faithful Catholic man ever said "I am willing to entrust my non-Catholic wife with the Catholic upbringing of our children if I'm no longer around to provide it".