Frontline is best and easiest, if you can't get a hold of any, you can also get tick removers you can get theese from the vet or good pet stores, they will only cost a couple of quid, tweezers will also work fine so long as you are carefull in slowly extracting the ticks from the ferrets skin (you need to make sure you get the whole tick out).
Remember to spray or wash out the ferrets bedding and living quarters, there might be more in there.
Don't use general cat or dog tick remover applications, the toxins in some of them can be to strong for ferrets.