First of, thank you everyone for the wonderful replies!
I can explain how that hairless rat in the picture you posted, with two furred parents was created. The rat is not a true genetic hairless it is in fact a double rex which can be bred through selective breeding to be mostly hairless - but they often still retain some facial hair and eyelashes which is vital as hairless are prone to eye issues (as they don't have eyelashes). Both parents had to of been rex (wavy/curly coat + whiskers), as its a dominant gene and if the rat carries it, it displays it. If you breed a rex rat to a standard coated rat, most of the litter will be rex (so its very easy to recreate). If you breed a rex to a rex... you will get a double rex which will have patchy hair. Through selective breeding you can then make them mostly hairless as seen in the picture. I hope thats easy to understand, I'm some what of a genetics freak when it comes to rats lol.
The true hairless often have issues producing milk, and the litter can die within the first few weeks because of it. As a pet breeder I am very careful which hairless lines I choose to breed because of this issue. They also have a naturally higher metabolism and eat about twice as much food, they don't need heat so much.. just provide a good little shelter for them like a cardboard box packed with kitchen paper towel or a hanging hammock.
Now if you have a double rex on the other hand, they don't have the higher metabolism so don't eat more food. They also don't need a heat source, I have found they do fine in a regular house temperature esp if housed with regular furred rats and again provided with nesting material. It is important any rats with any sort of baldness are not housed in chilly rooms or in a draft as they are more prone to illness.
I also want to give breeders a heads up on mega colon, which is created from ''high white'' markings. First let me explain mega colon, its basically where their bowels don't work right and they can't poop or if they can its very runny and strained. They generally don't grow the same rate as the other unaffected siblings and can look thin but bloated at the same time. 99% its not treatable and the rats suffer and die. The rare 1% it is, they need a special diet and care etc. And when you continue to breed from rats that produce offspring with megacolon, with each generation there will slowly be more and more in each litter that will get it and die. The affected babies will die before weaning and the effects are VERY visual from a young age. It is also possible the rats get late onset mega colon which is later in life anytime after 10 months of age. Its basically a rat with white where there shouldn't be. For example, facial blazes (stripes on the face) dots on the face etc. And any rat with odd color eyes I can guarantee you is capable of producing this deadly disease ... your best bet for healthiest babies is to stick to solid colored babies, or hooded markings. White bellies and feet are okay, but you don't want the white to be extending too far up the sides of the rat. I know people who produce for pet stores often aim for the high white look as it is pretty... but its also deadly!
As for the best way to break the neck... I believe you grab the body in one hand and the head in the other then quickly bring the neck backwards and up at the same time - so as to dislocate and break it for a quick painless death. You might want to research the technique a bit online. I'm not 100% sure as I've never had to do that myself.