2x? "sifted" media? Treat media before using?

[nogreenthumbs]

I've got 2 questions.

1. I keep seeing references to "sifted" media.

What's the sifting process/purpose?

Is this just the process of putting a large batch of media through screens of various size in order to separate them into small, medium, large?

2. Should I be doing anything to media before using it. I've seen some allusions to processing of some sort before use. I've got some mix that I got from a local orchid shop. It's orchiata, charcoal and perlite. I bought a bag and was given 2 smaller bags for free. The larger bag has a TON of dust in the bottom. I've been using the media out of the bag and then running a ton of water through the pots when I first pot with that media. I'm assuming that the prodigious amount of water that I run through is rinsing the dust out. Would you recommend doing anything else to the media, or doing something different to get the dust out or does it matter.

Most of the pots that I'm using are clear plastic orchid pots with slots on the sides and lots of slots in the bottom.