hi,
well, you've found yourself in a situation. sounds like the guy who sold the snakes wasn't of the highest character. care to share his name? he should have told you the snakes weren't taking food on their own, and you should have asked before buying. shame on you both; live and learn though.
so, what kind of snake are these babies? it matters, since it will indicate what sorts of things they might rather eat (insects, frogs, lizards, etc). how big/old are they? when did they last eat?
you may not have to resort to force-feeding at all (let's hope so). the fact that the snakes kill things is a good start. sometimes you get shy snakes that won't even strike, that's harder to work with. offering the right prey item, the right way, might cure your problem.
if you do end up needing to force-feed, or assist-feed, maybe you can use something other than mouse parts, that are easier to get in and down. lizards, for example, are a better shape than pinkies. if the patient isn't too far gone, i prefer to assist-feed rather than force-feed, so they get the taste of food in their mouth and they have to work their jaws and throat muscles. training the body before the mind, so to speak. mrs tt has a good webpage on assist- and force-feeding, showing the use of restraining tubes (you need to get or make yourself some of these tubes).
finally, don't give up hope, and don't rush into force-feeding. i've had baby and adult snakes i force- or assist-fed for over a year, that ended up taking food on their own and being good captives. but i always give snakes a couple of months, minimum, to eat on their own first. that usually works. success really depends largely on your determination to make things go your way, and your creativity in tricking or helping the snake do what you want.
cheers,
jimi