Definitely, you will want to rinse the Flourite many times with water before putting it into your aquarium. Otherwise, the dust it generates will make your aquarium very cloudy. Even with extensive rinsing, it will still make your aquarium look very murky for several days.
It should be washed until the water is nearly clear.
I think Flourite alone is the best substrate, but you can mix it with either sand of gravel.
For vacuuming the substrate, for most planted aquariums, people will simply hover a siphon over the surface of the substrate to collect any excess mulm. Similarly, uneaten food and waste can be vacuumed as above.
It should be washed until the water is nearly clear.
I think Flourite alone is the best substrate, but you can mix it with either sand of gravel.
For vacuuming the substrate, for most planted aquariums, people will simply hover a siphon over the surface of the substrate to collect any excess mulm. Similarly, uneaten food and waste can be vacuumed as above.