A dub tub is just two tubs inverted over one another. If you are purchasing stuff in bags and then dumping them in a tub that not really following a tek. Plus I guarantee you that any bag tek will take longer that the PF tek. Even an all in one bag will take longer if you are starting with spores. Check out grow from Wharfrat if you want teks from here on dubtubs, but the stuff here usually start from scratch and make their own subs and spawn themselves.
Please don't post links to shroomery here! Ask them for advice on their info on their site, thank you.