Yeah, it does like to dust alot.
Now for you 105 mixers.... If you guys are mixing stuff into 105 to get longer working times, you might want to look into M95. It has a nice, long working time, it's easy to use, and since you're not having to mix/cut it for the working time, it cuts just as well as 105. And it costs about half. Honestly, why pay so much for 105 if you're just defeating it's purpose? Megs intended it to be a very short working time, heavy cut compound, and you're paying *alot* of money for their efforts.
Using M105 in the manner in which Megs intended does work very well, it just takes alot of getting used to. Since 105 is capable of doing it's intended work in a short 15 seconds or so, why would you want to drag it out longer, and with less cutting? Yup, that sounds like a *perfect* job for much less expensive 95.