Fresh wedding flower bouquets start with the processing. I can't emphasize enough that using the right fresh flower products can truly extend the life of your fresh flowers. Professionals use this type of product and STILL have the advantage of a florist cooler for storage.
If you are a DIY bride, consider the flower products a big bonus on extending the life of your flowers - especially if they are at room temperature for a few days before the wedding.
Float soak your bouquet holder (that means you don't force it below the surface - you let it sink naturally as it soaks up water).
The European holder won't sink like other foam holders because of the large foam backer, but you need to still allow the foam several minutes to get completely saturated.
This is important because dry pockets can mean death for a few of your flowers if the stem happens to be in that pocket.