Which white did you use? I've never gotten on with the citadel whites, with ceramite white in particular always coming out lumpy and rough. I wasn't truly happy with any of my stormies, until I painted the Hoth Snowtroopers. For those I used Vallejo Gloss White and it was a massive improvement.
It gave a lovely smooth finish with enough natural reflection to not need a thin coat of varnish (e.g. Ardcoat) to produce a nice shine.