I'd be tempted to go for an injectable wormer too - that way you know for definate that they've had a dose (and the right dose for their weight

)
Or, to dose them orally mix up a dose for each in a big bucket and put them all in at the same time (2 people required though

)
Also, once you worm them, move them onto fresh ground if at all possible. Otherwise they'll just pick the worms back up again.
Are they permanent residents Yankiegirl ?
If they're going to slaughter you shouldn't need to do them again before they go - but if it's breeding stock it's definately worth getting regular worm counts done or bringing in a worming routine, otherwise their health will suffer and they won't be as happy, healthy and productive.
HTH
Karen x