I assume you're injecting them as opposed to using an oral treatment ?
Wait til they're eating, have a good strong gate between you and them (though that's maybe just cos we've recently done our boar

) Decide where you're jagging and go for it. Don't pussyfoot around or they'll start to get suspicious. Just stay calm and do it as quickly and with as little fuss as possible, keeping a good hold of the syringe (you don't want them running off with it still in them). You'll not get near them once you've done it, but by tomorrow they'll have forgotten all about it. Oh, and take spare needles - just incase you bend any !
HTH & good luck !
Karen