here's a good tip when building wheels, get a spare spoke and nipple and make one of these.
leave a few threads sticking out the end of the nipple then crimp the nipple to stop it turning. spoke the rim up but don't bother counting how many turns your giving each nipple, just keep them all loose. then use the tool you just made to go round the whole wheel tightening each spoke. the tool will bottom out when it hits the spoke
this makes sure that all the nipples are the exact same depth, then it's just a case of going round the wheel and tensioning the spokes. i've used this loads of times and i can do a wheel from start to finish in about 30-40 minutes.