Try to really plan ahead. (as you are doing now)
See if you can standardize as many parts as possible. That way you can learn on the first one, then save time doing the same thing again and again faster each time. My first roost took me about 4 hours, the second about 2.
The most important thing is the easiest:
Measure 2 times cut once. Try to have a plan written down, and if you dont have a good plan then do what I did:
Build a part, then mark the holes on the matching part. Dont try to piece things together by "guess-ta-measuring" sure you can get away with some of it on wood, but when I tied in some key components it didnt work well.
What works the best for me is taking the little time I have on weekdays and thinking about how to put stuff together. Draw pictures and line up uncut boards. Then on the weekend when there is real time go at it full tilt and build as much as possible.
You'll have time to learn as you go when you do that. Because no matter how good your plans are something always gets in the way.
Good luck!
(probably just a bunch of babble, but maybe something can help.)
