When the 3zz #3 (Period 3 = 34) appears, wait for the Trend Tool (or NonLagMA) to change to match the direction (counter-trend) and enter - e.g., if the 3zz appears below the candle in a downtrend, wait for the Trend Tool (or NonLagMA) to turn to its "go long" color and enter long.
Concerning repaint, I may be wrong from and EA standpoint, but it seems to me that it doesn't matter if the 3zz #3 repaints, as long as the EA code can read when it appears, and then enter and exit on the appearance. If it repaints and the entry parameters are not met, it should wait for the next 3zz #3 appearance and continuously check for Trend Tool (or NonLagMA) compliance for entry.
Exits should simply be when the opposite 3zz #3 appears. So it shouldn't matter if it repaints to a higher/lower level because the EA exit will happen on the first appearance. And then if it does repaint, you're automatically out of your long trade for instance, and it won't enter a short trade until Trend Tool (or NonLagMA)