Yeah, papercraft is very time consuming, and Captain Redbeard has a lot of parts!
The "trick" to building the hands I think, is to pre-shape the sides very well into the "C-shape" of the top and bottom, otherwise the tension in the paper will want to make the sides come loose again.
The outside of the hand should be convex, and the inside concave. If after pre-shaping you glue the two ends of the sides together, and it already has a good "C-shape" (like in step 25 of the LEGO Ghost: [link] ) it will be much easier to glue on the top and bottom of the hand.
I hope these tips will help you if you ever want to try it again; but in the meantime, I'm sure he won't be going anywhere so as long as you put the parts you already made somewhere safe, you can try it again whenever you like if you want to. ;O)