Cheapest way to get rid of fleas on my cat?

My suggestion is to maybe use some sort of Vaseline. I hear that It suffocates the fleas and kills them off. But that is if you can keep the cat still long enough to do this. The cat would also try to lick it off so I'm not sure, its just a suggestion. I'm trying to be some sort of help here but i don't believe I'm helping much. :) Hope things work out.