You can use this in the MES
Hi there and welcome!
Congrats on your 1st success!
Yeah a pellet smoking tube will work INSIDE your MES.
People recommend filling it half way up and then laying horizontal so the tube is filled half way longways because a full tube can produce more heavy smoke than wanted. The key is to get Thin Blue Smoke (TBS) not heavy white smoke. TBS is where the good smoke flavor is, not the heavy white smoke.
Also with pork butts, pork ribs, briskets, and chucks, they do not care what smoker temp you smoke/cook them at as long as you aren't burnign them. Additionally, these cuts of meat are only done when tender, never by time or temp.
So feel free to rock 275F smoker temp for those, and understand that the MES is likely not even hitting 275F temp. An accurate multi probe remote thermometer (4 probes or more is best) will let you know what your actual smoker temp is. MES units are ALWAYS off with their smoker and meat temp probes and almost always run low, never hitting 275F or your set temp.
Finally, not all pellets are created equal. Most brands are a blend of woods rather than 100% of the wood indicated on the label. So if you buy Pitboss Hickory you are getting something like 25-30% Hickory and the rest will be a cheaper hardwood like oak or alder.
They will try to fool you saying "100% hardwood pellets" which is true, its just not 100% hickory since oak is also a hardwood.
Or, they will say "100% all natural pellets no additives" which is not the same as 100% of the wood on the label.
Only brands like Lumberjack, Kingsford, or CookingPellets.com (maybe a couple of other brands but few and far between) will indicate that it is 100% of the wood on the label or indicate it is a BLEND.
Ask all the questions you have, lots of us MES owners are here and lots of amazing smoking and cooking knowledge in this community :D