Not real sure man.. you had to ask..lol. There are different techiques I have read about. I did alot of resaerch after I wasnt please with my DIY version. For me you either smell it or you don't. There is no middle ground.. I know some hydro shops offer refilling service and they use a vibrating table. Others I have talked to recommended filling it while there was a sander attached to created vibration and filling it slowly.
I mean obviously the point is to use the best carbon as it is usually more refined in size/shape. All activated carbon is not created equal..not even close...Also, you want to back it as tight as possible by whatever means...Also the slower you pull through the scrubber the better as the activated cabon has more time to react with the air traveling through it...
I have heard can-filter usies a hydrolic press, but am not certain. There was some discussion in this at the following link..
Cannabis and Marijuana seeds :: HomeGrown420 - Carbon Scrubber anybody?