As far as I remember, the ADDIEM uses a TWFK variant. Cosmic Ears uses their own custom twin BA driver, not a TWFK. So it won't be the same.
Regarding DIY impressions - I've done my own for all but my first few pairs of customs. It seems easy enough that even I can do it, which is saying a lot. Over a dozen sets of CIEMs have turned out well based on my own impressions, and in fact I've had far less trouble with fit since I started doing it myself. I don't want anyone to do something they aren't comfortable with, but it really is very easy to do, and is at least worth a try in my opinion. You can always follow up with professional impressions if you can figure it out for yourself.