I'm going to disgorge here, please feel free to critique or add to as you may see fit, anyone.
About rinsing Flourite: I use a paint strainer bag from the Borg. I fill the strainer bag, rinse for a minute or two in a 5-gallon bucket. Never had real isses with it. I did this two weeks ago and added an entire bag of Flourite over Profile in an existing tank without removing fish or plants. I added it by handfuls after rinsing, did some minor rearrangement of the plants and finished with a 50% water change.
A shot of the bag:
I'll be doing this for Onyx sand most likely tonight if I get down to the Petshmart today. Everyone has some good ideas about handling the dust in Flourite. Here's what I would do if I were you:
-rinse the Flourite
-drain the tank into the keeper containers
-place fish and plants in containers
-drain the entire tank, get all the water out possible
-remove the UGF
-add as much Flourite as you want to mix into the gravel and mix it. If you want, it might work a little better to cap with some Flourite after mixing.
-gently refill to the level you like best for replanting and replant
-top the tank up with water. Entire process to this point might take two hours, depending on what and how much you have to plant.
-add fish whenever you like. If done right, they should be back in within a few hours.