Yes, it is entirely possible to introduce two males to one female at breeding time, and she can (and most likely will) be fertilized by both of them. The eggs will be sired by two different males and will be half-siblings to each other. The trick is to do this with males that will either make no difference as to parentage, or males that will easily be identifiable as the sire from the eggs.
For example, if I have 2.3 okeetees, I can breed both males to all three females, and it does not matter at all which male sired which hatchling, because they are all okeetees. But what if I used one okeetee male and one amel male? If none of the females are het for amle, then all of the babies will look pretty much the same (some might have more okeetee looking characteristics than others, but I would suspect that it would be no more variation than could be found in any straight okeetee clutch), and there would be no way for them to be identified as being okeetee or okeetee het for amel.
However, I have a lavander female. Let's say that I will breed her to my lavander male AND to my motley snow corn. If the hatchlings come out lavs, I know who the sire was, and if they come out normals, I know their sire too. These normals will obviously be het for lav, amel, anery, AND motley, and I can sell them as guaranteed hets because I KNOW for a fact where they came from.
Exposing a female to two or more males is great for a couple of reasons. First, it allows for more diversity in your clutches ( I would definitely let the male you most want babies from have first crack at her, though); second, it encourages breeding activity because the scent of another male will enhance the need to breed in many males (competition, you know); third, it will increase the number of fertile eggs that your female will through. This is especially true if your male is young or a poor percentage breeder; fourth, it's just too fun to wait and see what comes out of those eggs after you've planned and charted all the possibilities!
By the way, as long as a female is in good flesh, there is absolutely no reason in the world to double clutch her. To say that going for a second clutch is money grubbing, but the first clutch isn't is a little dubious an argument, I would think. After all, unless you're building up your own personal collection with the hatchlings, don't we all intend to sell those babies? If a female takes a double clutch, fine; if not, fine. However, I've never had a problem doing this, and yes, I do sell those babies too. Am I selling those animals for a profit? Yes. Does that make me someone that is in it for the profit only? No.