Issues with applying liquid flea/worm treatment on a 4kg+ cat

Hey everyone,

Fairly new cat owner here. May I please know what I am doing wrong when I am applying this liquid flea/worm treatment monthly on my cat as instructed. I can get it to the skin fairly well I think but after I let go of my cat he just shakes his head and I find some of the liquid coming off.

I tried keeping him in my arms this time for about a minute but that didn't really dry the liquid either and the same thing happened. Obviously I have not reapplied and I have cleaned the surfaces and also washed my hand thoroughly so it is not ingested.

Thanks