NOOOOOO!!!!!!!!! What ever you do, dont feed a retic, burm, rock, conda, ect, outside of their enclosure. A few reasons, one is after its done eating the handleing to get it back into its enclosure could cause it to regurge. A second reason is that animals with heavy feeding responces (retics would be famous for this) can often stay in "feed mode" for several hours to even a day or two. What this means is that if they smell that food, and that switch is flipped, anything and everything that moves or is warm is, in their eyes, food (ie dead!) you do not want this when you have a 10, 12, 16, or bigger animal. Lastly if you take it out to feed it, then yes it will not associate you sticking your hand in with food, insted it will think that every time you take it out there will be food, and that switch will be flipped.
Feed the snake in its cage. Just hook train it and you will be fine. The way you do this is, every time you go in the cage to do something thats not feeding (clean, change water, check temps, take him/her out, ect) you will gently tap or rub the animal on the top of the nose. When my animals are young I rub them for a few seconds with the hook, until they get it, then after a few weeks I cut it down to just a single tap. What this does is get the aniaml to associate the hook tapping them as "no food buddy, so dont bite," another thing this does is, if you startle the snake or it is just having a real bad day, your hook will get tagged insted of your hand.
Now when you go to feed, most likely you will use tongs to feed the snake, do not let the snake see the tongs unless you are going to feed, and if you are feeding, dont let it see the hook. When you feed, open the cage and present the food item, do not tap it with anything first. Do this and you should be fine
Note: While its called hook training and typicaly a hook is used, you dont need to use a hook, The hook is only to allow distance between you and the snake for that fist touch. Anything thats long enough and wont hurt the snake is fine. I have a 30in hook and an 18in hook, but also use empty paper towel rolls, pop bottles, a hanger, and once I used my shoe.