I always worm my kittens at 2,4,6,8,+ weeks,i either use mashed up kitten meat,or soaked kitten biscuits mashed up.Some take to it quicker than others.Try smearing a little food on his lips/paws so he licks it off,to get the taste.you could also give a milk substitute(from vets)which you can give on its own and use to mash foods with.