they key is to use an active carbon filter and make sure your tent or grow area has negative pressure -- smell cannot leak out before the filter as long as there is negative pressure... air is only pulled into area and cannot escape except through your exhaust fant. Easier to do with a tent than a room due to smaller volume.
If the walls bow in slightly, you have negative pressure. you do not need to make it bow in so much that you lose space inside. Just make sure it's a pull and not a push from air pressure inside. Slowly adjust exhaust fan until you achieve it. Can always put up some makeshit support bars between tent poles to hold the walls out, if necessary.
not all carbon filters are of the same quality. some come with more (grams) activated carbon, and those will be more effective and last longer. Contact manufacturer for that information. Some can be refilled and that would be the cheapest option in the long run.
Pay attention to the rated CFM of the filter. In general, a 6" filter and 6" duct exhast fan should match up, but maybe some cheap shit out there will not. If you go over rated cfm of the filter, it will be less effective. Best to buy duct fans you can run at 50% or less anyway to reduce noise and stress on the duct fan.
review - negative pressure, carbon filter... done.
Sorry i can't help with best brands to buy. The smell from my tent is a point of pride. :P