Leafshine Plant Polish
Florist usually use a product that is called "plant polish". Just as the name implies, greenery that comes straight from the farm has been packed in bunches and is briefly rinsed.
Hard water tends to leave the greenery with a splotchy white residue. Leafshine gives the greens a slick shiny finish that looks so much better.
No matter what product you use, if it comes in an aerosal can you need to keep the nozzle a distance away from your greens or flowers. The propellant used in the can is very cold and can freeze fresh flowers.
I used to sell smaller cans, but the manufacturer quit making them. The product can also be used safely on plants and other greenery. This product isn't a must - but I do use it on every greenery design I make.
Just be sure to spray the greenery before adding flowers - use a flower sealant (like Finishing Touch) for sealing the flowers.