Have found best thing is frontline( same as for dogs) can get it from normal vets in pump/spray bottle for under £30. spray it on and once dried it is safe ie, grooming.It lasts for upto three months. its extremely good. did use the powder but found it not to be too good.
My lad was covered in them when he was a baby,i bought one from a tack shop and it worked a treat(was years ago mind,lol,half the ingredients have probably been taken out these days,lol)I would say you will probably be better off with the frontline these days,things have come on sooo much!!God i sound old and am only 32,lmao
!!(however when i used the powder years ago nothing else had them!!!)
I have some stuff in a white and gold tin, for farm animals and horses. Can't remember the name but it does work, got rid of fleas on the cat as well. Its made with pyrethrin which is a flower, so no nasty chemicals either.