I have found the dust/chips don't last long. I use chucks, and slabs of hickory off a friends tree. Also, you really don't want a lot of smoke...you want TBS not a lot of bilowing white stuff.
You can prolong the smoke off dust or chips by putting them in a pouch made of tinfoil with a few holes poked in the sides. I find they smolder better that way, and don't just light on fire. Though they still don't last as long as chunks.
Maybe it's just me but I've never liked the smell of smoldering sawdust. Smells too much like burning paper or cardboard. I like to use chunks. If I had a chipper/shredder I would try running it through that also. The smoke seems to smell better off of "real" wood.
I also have a GOSM wide body. I use a combination ...... I put some chips in the bottom of the smoke try and then chunks on top. The chips get started smoking quicker and then help the chunks get going for the long stretch. I have found that if I use the chips alone, they burn up too fast..... have to keep opening the door to restock them. Chunks rule for me.