This is a bunch of technic parts along with some manuals, but the sets aren't 100% complete.  Should I sell the different boxes separately, like "power functions" then "pins" etc?

 

Or should I sell it all as one big Technic lot?  Opinions are welcome.

 

 

 

there seem to be at least 3 good sets (4x4, Unimog, 7900) in there, which I would try to retrieve. With the same number of total pieces in a set, the number of different pieces is significantly smaller in Technic sets compared to regular Lego.

Print the parts list off bricklink (or copy the pages from instructions), get a pack of zip-lock bags and try to take out at least the three sets I mentioned, sort them roughly by kind (axles, pins, gears, beams, wheels) and sell them as checked completed. I've done this with similar sized lots, it's work, but not as much as you may think.

Also the limited amount of different pieces means that you are often lucky getting missing from the lesser sets in a lot. You can still sell the remaining pieces as a lot.

May I ask how much you payed for this?