What compound should be used for base skim coat?
I've been a drywall pro for 30+ years and I currently run my own drywall repair business.  Since I mostly do very small jobs and repairs I have found ONE product that I use for everything that calls for non fast setting drywall mud, and that is a product called Plus 3, by USG.  You might not find that exact product in your area, but try looking for a lightweight all purpose.  The reason I use this is it has low shrinkage, works well for taping, coating, and texturing.  I spray it for orange peels, etc, and hand apply textures like skip trowel, and it does it all well.  I dislike green lid all purpose for anything except taping as it's harder to sand and shrinks more.  

I do us a LOT of durabond type products, although I use the USG Easy Sand 5,20 or 45 minute hot mud. Note that durabond is a brand name used by many like kleenex is used for tissue paper.  Here, we often use the term hot mud instead.  But I would ONLY recommend it if you are very skilled since it is VERY hard to sand, despite the name of easy sand.  Although in thin layers it sand ok.  But if you apply too much it's pretty difficult to sand off, whereas the Plus 3 is incredibly easy to sand.  And the hot mud costs much more, is difficult to mix up requires constant cleaning of tools every 20-90 minutes, and can give you fits with lumps, etc.  Box mud mixes easily, goes on smooth, and sands easy. 

The reason to use hot mud is the faster it sets up the less it shrinks, and the quicker you can apply the next coat.  But I almost always finish the final coat with plus 3 for ease of sanding.