Cotton also expands a fair bit once It's had juice in it for a time, that being said I've never had an issue with cotton at first, only after a day or two when I usually replace it
I just rip a randomly guessed amount off a cotton ball, roll it loosely and try and shove it in my coil, if it doesn't slide right in I take it out and take a tiny amount off or roll it tighter, seems to work great, and since I boiled it I only get that 'cotton taste' for maybe a puff or two if at all (maybe I'm just used to it and don't notice it)
I don't/never have used an evod though so it's hard to tell exactly what you're doing wrong without actually seeing you do it
another thought is that it could be the coil, or not enough juice in the cotton, it has to be saturated all nice and goodlike (I normally use like 10-15 drops to prime mine probably more)