The only real way is to flat it down with some really fine grade wet 'n dry then that is wet and then buy a can of spray on clear laquer and make a few passes at it just to seal it. It won't be a great finish but it will stop it getting worse.
HTH
Niz406
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"Some Say he can fart fire, whilst others say he can urinate rocket fuel.... all we know is he's called... The Niz"