Yes, you can breed a female twice, however, it's not recommended. They spend a lot of energy laying eggs and if you have them double clutch, they don't have a chance to regain that weight. Another thing to consider is that not all corn snakes will give you two clutches and some will give you two clutches without you reintroducing a male. It's really all dependent on the female.
As for feeding, I feed all my corn snakes mice from the Munson plan (http://medusa-corns.webs.com/feedingchart.htm). It has worked out well for me thus far and I plan to continue to use it. You can, however, feed rats, but if you do, I'd advise you to use this chart on when to start feeding rats (http://i584.photobucket.com/albums/s...mousesizes.jpg) You can also go by prey weight. Some pinky rats are MUCH larger than fuzzy mice (more like hopper mouse size). Whatever is easier for you.
As for what morphs to use, I would HIGHLY suggest you look at what you want to breed for. There are only a handful of morphs that are dominant morphs. 95% are recessive so when you start buying snakes, make sure to take into account what they are het for!
I will be breeding my corn snakes this time next year. I'm working with the following adults: anery motley het amel male, snow female, bloodred het hypo/lavender/motley PH amel and caramel, hypo lavender PH motley male, and a miami phase female. I plan on pairing my anery with the snow and the bloodred with the hypo lavender (my long term project is hypo lavender bloodreds). My miami phase has no breeding plans for her but I may buy her a miami boyfriend eventually.
Also, follow the rule of threes when breeding: females need to be three feet long, three years old, and three hundred grams.
Best of luck!