After you have roughened the surface either with scotchbrite or fine wet and dry paper used wet it is best to clean the the surface with panel wipe.

This is what is used by all auto body repair shops to clean the surface after rubbing down and before spraying.

You can buy a gallon of panel wipe from any Auto paint outlet for a few pounds and it lasts you for years.

Also ideal for cleaning/degreasing of any kero stains at the end of a days flying.

Phil.