Females lay multiple eggs. While each egg can be fertilized by only one sperm, if there are multiple sires then either sire could be the father of a particular egg.
So, you have a pinstripe female and two potential sires: a mojave and a spider. On alternating weeks you put a different male into the female's tub. One male may sire some of the eggs, the other male the rest of the eggs.
Of course, you don't want to do this where one male is a visual recessive and the other isn't, as you wouldn't know which babies were hets and which were not. For doms/codoms you can play the "who's your daddy" game.