When I build wheels, the first thing is make sure all threads are oiled. Then worry about is roundness, get that first, then get it straight side to side and finally work on tension. Each spoke is not going to be at perfect tension, just make sure the average is near the spec you're using.

The last thing I do is stress the wheel. I put the wheel on the ground and put one foot on the rim. Then I balance myself with the end of a table and with the other foot, I GENTLY apply pressure until I can just feel the rim start to give a little. Lots of pings and pops. Go around that side, then flip it over and do the same on the other side. Then I put it back in the truing stand and true it and stress again. Repeat until you can stress the wheel and it doesn't go out of true. I've had wheels that I haven't had to true in years using this method.