How do you cover up a posh accent?

You can reform your accent, but be careful. People who change their speech because they feel that their pronunciation of some sounds is "wrong" are very likely to over-correct, resulting in hideous monsters of mispronunciation. For example, many in America think that saying styudent is better than saying stoodent. People who would normally say stoodent can teach themselves to say styudent - but it will also cause them to say nyune instead of noon.