A good solvent cleaning should cure it. Brake cleaner or the like.
A normal rule of thumb is to size bullets 0.001" to 0.002" over groove diameter for least leading and best accuracy, so I would look for a .453" sizer if you are going to size them. In general, too big is better than too small, because too small tends to allow gas bypass and cutting of the bullet base that can introduces further leading and spoil accuracy.